[Z06] Trouble code help!
Tech Contributor
Joined: Oct 1999
Posts: 41,066
Likes: 9,832
From: Charlotte, NC (formerly Endicott, NY)
The C1278 is due to the PCM codes (more than likely the throttle position ones since they might affect traction control). When certain PCM DTCs are set, the PCM will not be able to perform the torque reduction portion of traction control. A serial data message is sent to the EBCM indicating that traction control is not allowed.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The PCM diagnoses a condition preventing the engine control portion of the traction control function and sends a serial data message to the EBCM indicating that torque reduction is not allowed. The PCM will typically set a DTC and the EBCM will set this DTC.
Action Taken When the DTC Sets
If equipped, the following actions occur:
The EBCM disables the TCS/VSES for the duration of the ignition cycle.
The Traction Control and Active Handling indicator turns ON.
The DIC displays the following messages:
Service Traction System
Service Active Handling
The ABS remains functional.
DTC P0140 or P0160
Circuit Description
The powertrain control module (PCM) supplies a voltage of approximately 450 mV between the heated oxygen sensor (HO2S) high and low signal circuits. The oxygen (O2) sensor varies the voltage from approximately 1,000 mV when the exhaust is rich, through approximately 10 mV when the exhaust is lean.
The PCM monitors and stores the heated oxygen sensor (HO2S) voltage information. The PCM evaluates the HO2S voltage samples in order to determine the period of time during which the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period, and determines if the majority of the samples are out of the operating range.
The PCM monitors the HO2S voltage and detects if the voltage goes out of the bias range. If the PCM does not detect that the voltage went out of the bias range, a DTC sets.
Conditions for Running the DTC
DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0135, P0141, P0155, P0161, P0200, P0300, P0410, P0440, P0442, P0446, P0452, P0453, P1120, P1125, P1220, P1221, P1221, P1258, P1415, P1416, P1441, P1514, P1515, P1516, P1517, or P1518 are not set.
The engine run time is more than 409 seconds.
The ignition 1 signal is between 9-18 volts.
The loop status is Closed.
The secondary air injection (AIR) and the catalyst diagnostics are not active.
Conditions for Setting the DTC
The HO2S signal voltage is steady between 409-489 mV for 145 seconds.
The throttle position (TP) indicated angle changes more than 5 percent within 1 second, 6 times.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Important
Before you service the PCM and throttle actuator control (TAC) module, remove any debris from the module connector surfaces. Inspect the module connector gaskets when you diagnose or replace the modules. Ensure that the gaskets are correctly installed. The gaskets prevent contaminate intrusion into the modules.
For any test that requires probing the PCM or probing a component harness connector, use the connector test adapter kit J 35616-A . Using this kit prevents damage to the harness and component terminals. Refer to Using Connector Test Adapters in Wiring Systems.
An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provides the supply of oxygen. Inspect the HO2S wires and connections for breaks or for contamination. Refer to Wiring Repairs in Wiring Systems.
For an intermittent condition, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
The engine must be at the normal operating temperature before you perform this test.
Using the Freeze Frame and/or Failure Records data may help to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help to determine the number of miles since the DTC set. You can also use the Fail Counter and the Pass Counter in order to determine how the number of ignition cycles in which the diagnostic reported a pass and/or a fail. Operate the vehicle within the same Freeze Frame conditions that the PCM recorded, including the RPM, the load, the vehicle speed, and the temperature. This procedure isolates when the DTC failed.
If the scan tool indicates that the HO2S voltage goes below 200 mV, this indicates the HO2S circuits and PCM are OK.
This step verifies whether the low signal circuit from the PCM is OK. A voltage indicates that the PCM and the wiring are OK.
This step verifies whether the signal circuit from the PCM is OK.
Disconnecting the PCM allows you to use a DMM in order to test the circuit continuity. This procedure helps to locate an open or shorted circuit.
Step
Action
Values
Yes
No
Schematic Reference: Engine Controls Schematics
1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Important
Inspect the HO2S for being secure before proceeding with this DTC. A loose sensor could cause this DTC to set.
Install a scan tool.
Start the engine and idle the engine at the normal operating temperature.
Operate the engine above 1200 RPM for 2 minutes.
Observe the HO2S voltage with a scan tool.
Does the HO2S voltage vary outside the specified range?
350-550 mV
Go to Step 3
Go to Step 4
3
Observe the Freeze Frame and/or Failure Records data for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame and/or Failure Records data that you observed.
Does the DTC fail this ignition?
--
Go to Step 4
Go to Intermittent Conditions
4
Turn ON the ignition, with the engine OFF.
Disconnect the HO2S.
Jumper the HO2S high signal circuit to a known good ground.
Jumper the HO2S low signal circuit to a known good ground.
Observe the HO2S voltage with a scan tool.
Is the HO2S voltage below the specified value?
200 mV
Go to Step 8
Go to Step 5
5
Remove both jumper wires.
Use the DMM in order to measure the voltage from the HO2S low signal circuit to a battery ground.
Is the voltage near the specified value?
5V
Go to Step 6
Go to Step 7
6
Turn OFF the ignition.
Disconnect the PCM connector C1. Refer to Powertrain Control Module (PCM) Replacement .
Test for continuity of the HO2S high signal circuit. Refer to Testing for Continuity in Wiring Systems.
If no continuity is indicated on the DMM, repair the open circuit. Refer to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 10
7
Turn OFF the ignition.
Disconnect the PCM connector C1. Refer to Powertrain Control Module (PCM) Replacement .
Test for continuity of the HO2S low signal circuit. Refer to Testing for Continuity in Wiring Systems.
If no continuity is indicated on the DMM, repair the open or the faulty connection Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 10
8
Inspect the HO2S circuits for a faulty connection at the HO2S harness connector. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.
If you find a faulty connection, replace or repair the terminal as necessary. Refer to Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 9
9
Replace the affected HO2S. Refer to Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 2 .
Did you complete the replacement?
--
Go to Step 12
--
10
Inspect the HO2S circuits for a faulty connection at the PCM. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.
If you find a faulty connection, replace or repair the terminal as necessary. Refer to Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 11
11
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?
--
Go to Step 12
--
12
Use a scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?
--
Go to Step 13
Go to Step 2
13
With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List
System OK
DTC P1220
Circuit Description
The throttle position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. Two separate signal, low reference and 5-volt reference circuits are used in order to connect the TP sensor assembly to the throttle actuator control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage is pulled up to the reference voltage as the throttle opens, from below 1 volt at closed throttle to above 3.5 volts at wide open throttle (WOT). The TP sensor 2 signal voltage is pulled down to the low reference from around 3.8 volts at closed throttle to below 1 volt at WOT. TP sensor 1 and APP sensor 1 share a 5-volt reference circuit that is connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that is connected within the TAC module. If an out of range condition is detected with the TP sensor 2, this DTC will set and the Reduced Engine Power message will be displayed.
Conditions for Running the DTC
DTCs P1517, or P1518 are not set.
The ignition switch in the crank position or run the position.
The ignition voltage is greater than 5.23 volts.
Conditions for Setting the DTC
The TP sensor 2 voltage is less than 0.13 volts or greater than 4.87 volts.
All above conditions present for less than 1 second.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Inspect the throttle actuator control (TAC) module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing.
When the TAC module detects a condition within the TAC System, more than one TAC System related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
If this DTC is determined to be intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Using a test lamp reduces the amount of current fed into the signal circuit. The scan tool should display the maximum value for this parameter, 5-volts even though the actual voltage is higher.
The TP 2 sensor and the APP 2 sensor share a common 5 volt reference. The 5-volt reference circuits are connected internally within the TAC module. Disconnecting the TAC module will isolate the 5-volt reference circuits.
The TP sensor 2 and the APP sensor 2 share a common 5-volt reference. A short to voltage on the APP sensor 2, 5-volt reference circuit will affect the TP sensor 2, 5-volt reference circuit.
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This condition is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
DTC P1220 - Throttle Position (TP) Sensor 2 Circuit Step
Action
Values
Yes
No
Schematic Reference: Engine Controls Schematics
1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Is DTC P1515, P1516, or P1518 also set?
--
Go to Diagnostic Trouble Code (DTC) List
Go to Step 3
3
Turn OFF the ignition.
Remove the air inlet duct from the throttle body assembly.
Disconnect the throttle actuator motor harness connector.
Turn ON the ignition, with the engine OFF.
Manually close the throttle blade completely while observing the TP sensor 2 voltage parameter on the scan tool.
Does the scan tool indicate that the TP sensor 2 voltage is within the specified values?
4.3-4.8 V
Go to Step 4
Go to Step 7
4
Open the throttle blade to wide open throttle (WOT) by hand while observing the TP sensor 2 voltage parameter on the scan tool.
Does the scan tool indicate TP sensor 2 voltage within the specified values?
0.13-1 V
Go to Step 5
Go to Step 7
5
Turn OFF the ignition for 15 seconds.
Reconnect the throttle actuator motor harness connector.
Reinstall the air inlet duct.
Turn ON the ignition with the engine OFF.
Select the DTC Info. option on the scan tool.
Lightly touch and move the related engine wiring harnesses and connectors for the TP sensor while observing the DTC Info. The DTC will set if an intermittent condition is present. Refer to Testing for Intermittent and Poor Connections and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 6
6
Continue to observe DTC Info.
Slowly depress the accelerator pedal to WOT and then slowly return the pedal to the released position 3 times.
Does the scan tool indicate this DTC failed this ignition?
--
Go to Step 26
Go to Diagnostic Aids
7
With a scan tool, observe the TP sensor 2 voltage parameter.
Does the scan tool indicate that the TP sensor 2 voltage is at the specified value?
5 V
Go to Step 8
Go to Step 12
8
Disconnect the TP sensor harness connector.
Does the scan tool indicate that the TP sensor 2 voltage is at the specified value?
0 V
Go to Step 9
Go to Step 13
9
Disconnect the APP sensor harness connector.
Turn ON the ignition with the engine OFF.
With a DMM, test the TP sensor 2, 5-volt reference circuit for voltage.
Does the DMM indicate voltage near the specified value?
5 V
Go to Step 10
Go to Step 18
10
With a DMM connected between the TP sensor 1 low reference circuit and the TP sensor 2 low reference circuit at the TP sensor harness connector, test for resistance
Does the DMM indicate resistance within the specified values?
0-5 ohms
Go to Step 14
Go to Step 11
11
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the TP sensor circuits.
With a DMM, test the TP sensor 2 low reference circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 32
12
Disconnect the TP sensor harness connector.
Connect a test lamp between the TP sensor 2 signal circuit and the battery positive voltage.
Does the scan tool indicate TP sensor 2 voltage near the specified value?
5 V
Go to Step 20
Go to Step 15
13
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the TP sensor circuits.
Turn ON the ignition.
With a DMM, test the TP sensor 2 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 17
14
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the APP sensor circuits.
Turn ON the ignition with the engine OFF.
With a DMM, test the APP sensor 2 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 24
15
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the TP sensor circuits.
With a DMM, test the TP sensor 2 signal circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 16
16
With a DMM, test the TP sensor 2 signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 17
17
With a DMM, test for a short between the TP sensor 2 signal circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 32
18
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the TP sensor circuits.
Turn ON the ignition with the engine OFF.
With a DMM, test the TP sensor 2, 5-volt reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 19
19
Turn OFF the ignition.
Disconnect the other TAC module harness connector.
Turn ON the ignition with the engine OFF.
With a DMM, test the APP sensor 2 5-volt reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 24
20
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the TP sensor circuits.
With a DMM, test the TP sensor 2 5-volt reference circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 21
21
With a DMM, test the TP sensor 2 5-volt reference circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 22
22
Disconnect the APP sensor harness connector.
Disconnect the other TAC module harness connector.
Turn ON the ignition with the engine OFF.
With a DMM, test the APP sensor 2 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 23
23
With a DMM, test the APP sensor 2 5-volt reference circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 24
24
With a DMM, test the TP sensor 2 5-volt reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 25
25
With a DMM, test for a short between the TP sensor 2 5-volt reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 26
26
With a DMM, test for a short between the APP sensor 2 5-volt reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 27
27
With a DMM, test the TP sensor 2 signal circuit for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 28
28
With a DMM, test the TP sensor 2 low reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 29
29
Reconnect the TAC module connectors.
Turn ON the ignition.
With a DMM, measure voltage at the TP sensor 2, 5-volt reference circuit.
Does the DMM indicate voltage greater than the specified value?
6.06 V
Go to Step 32
Go to Step 30
30
Turn OFF the ignition.
Connect a test lamp between APP sensor 2, 5-volt reference and battery positive voltage.
Does the test lamp illuminate?
--
Go to Step 32
Go to Step 31
31
Inspect for poor connections at the TP sensor harness connector. Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 33
32
Inspect for poor connections at the TAC module harness connector. Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 34
33
Important
The throttle position sensor is not a serviceable part and should only be replaced with the throttle body assembly.
Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .
Did you complete the replacement?
--
Go to Step 35
--
34
Replace the TAC module. Refer to Throttle Actuator Control (TAC) Module Replacement .
Did you complete the replacement?
--
Go to Step 35
--
35
Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?
--
Go to Step 36
Go to Step 2
36
With a scan tool, observe the stored information, Capture Info.
Does the scan tool indicate any DTCs that you have not diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List
System OK
DTC P1221
Circuit Description
The throttle position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. Two separate signal, low reference and 5 volt reference circuits are used in order to connect the TP sensor assembly to the throttle actuator control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage is pulled up to the reference voltage as the throttle opens, from below 1 volt at closed throttle to above 3.5 volts at wide open throttle (WOT). The TP sensor 2 signal voltage is pulled down to the low reference from around 3.8 volts at closed throttle to below 1 volt at WOT. TP sensor 1 and APP sensor 1 share a 5-volt reference circuit that is connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that is connected within the TAC module. If an out of range condition is detected with the TP sensors, this DTC will set and the Reduced Engine Power message will be displayed.
Conditions for Running the DTC
DTCs P1517, or P1518 are not set.
The ignition switch is in the crank or run position.
The ignition voltage is greater than 5.23 volts.
Conditions for Setting the DTC
TP sensor 2 disagrees with TP sensor 1 by more than 7.5 percent.
All above conditions are present for less than 1 second.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing.
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
If this DTC is determined to be intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
DTC P1221 - Throttle Position (TP) Sensors 1, 2 Performance Step
Action
Yes
No
Schematic Reference: Engine Controls Schematics
1
Did you perform the Diagnostic System Check-Engine Controls?
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Is DTC P1518 also set?
Go to Diagnostic Trouble Code (DTC) List
Go to Step 3
3
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the TP sensor 1 and 2 Agree/Disagree parameter.
Does the scan tool TP sensor 1 and 2 Agree/Disagree parameter indicate Disagree?
Go to Step 5
Go to Step 4
4
Remove the air inlet duct from the throttle body.
Disconnect the throttle actuator motor harness connector.
Slowly manually open the throttle blade to WOT and back to the closed throttle position several times while observing the scan tool TP sensor Agree/Disagree parameter.
Does the TP sensor Agree/Disagree parameter change from Agree to Disagree during the above test?
Go to Step 18
Go to Step 5
5
Disconnect the TP sensor harness connector.
Disconnect the TAC module harness connectors.
Test the TP sensor 1 5-volt reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 6
6
With a DMM, test for a short between the TP sensor 1 5-volt reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 7
7
With a DMM, test the TP sensor 1 signal circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 8
8
With a DMM, test for a short between the TP sensor 1 signal circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 9
9
With a DMM, test the TP sensor 1 low reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 10
10
With a DMM, test for a short between the TP sensor 1 low reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 11
11
With a DMM, test the TP sensor 2 5-volt reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 12
12
With a DMM, test for a short between the TP sensor 2 5-volt reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 13
13
With a DMM, test the TP sensor 2 signal circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 14
14
With a DMM, test for a short between the TP sensor 2 signal circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 15
15
With a DMM, test the TP sensor 2 low reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 16
16
With a DMM, test for a short between the TP sensor 2 low reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 17
17
Inspect for poor connections at the harness connector of the TAC module. Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 18
18
Inspect for poor connections at the harness connector of the TP sensor. Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 19
19
Important
The throttle position sensor is not a serviceable part and should only be replaced with the throttle body assembly.
Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .
Did you complete the replacement?
Go to Step 20
--
20
Use a scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?
Go to Step 21
Go to Step 2
21
With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?
Go to Diagnostic Trouble Code (DTC) List
System OK
Bill
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The PCM diagnoses a condition preventing the engine control portion of the traction control function and sends a serial data message to the EBCM indicating that torque reduction is not allowed. The PCM will typically set a DTC and the EBCM will set this DTC.
Action Taken When the DTC Sets
If equipped, the following actions occur:
The EBCM disables the TCS/VSES for the duration of the ignition cycle.
The Traction Control and Active Handling indicator turns ON.
The DIC displays the following messages:
Service Traction System
Service Active Handling
The ABS remains functional.
DTC P0140 or P0160
Circuit Description
The powertrain control module (PCM) supplies a voltage of approximately 450 mV between the heated oxygen sensor (HO2S) high and low signal circuits. The oxygen (O2) sensor varies the voltage from approximately 1,000 mV when the exhaust is rich, through approximately 10 mV when the exhaust is lean.
The PCM monitors and stores the heated oxygen sensor (HO2S) voltage information. The PCM evaluates the HO2S voltage samples in order to determine the period of time during which the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period, and determines if the majority of the samples are out of the operating range.
The PCM monitors the HO2S voltage and detects if the voltage goes out of the bias range. If the PCM does not detect that the voltage went out of the bias range, a DTC sets.
Conditions for Running the DTC
DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0135, P0141, P0155, P0161, P0200, P0300, P0410, P0440, P0442, P0446, P0452, P0453, P1120, P1125, P1220, P1221, P1221, P1258, P1415, P1416, P1441, P1514, P1515, P1516, P1517, or P1518 are not set.
The engine run time is more than 409 seconds.
The ignition 1 signal is between 9-18 volts.
The loop status is Closed.
The secondary air injection (AIR) and the catalyst diagnostics are not active.
Conditions for Setting the DTC
The HO2S signal voltage is steady between 409-489 mV for 145 seconds.
The throttle position (TP) indicated angle changes more than 5 percent within 1 second, 6 times.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Important
Before you service the PCM and throttle actuator control (TAC) module, remove any debris from the module connector surfaces. Inspect the module connector gaskets when you diagnose or replace the modules. Ensure that the gaskets are correctly installed. The gaskets prevent contaminate intrusion into the modules.
For any test that requires probing the PCM or probing a component harness connector, use the connector test adapter kit J 35616-A . Using this kit prevents damage to the harness and component terminals. Refer to Using Connector Test Adapters in Wiring Systems.
An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provides the supply of oxygen. Inspect the HO2S wires and connections for breaks or for contamination. Refer to Wiring Repairs in Wiring Systems.
For an intermittent condition, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
The engine must be at the normal operating temperature before you perform this test.
Using the Freeze Frame and/or Failure Records data may help to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help to determine the number of miles since the DTC set. You can also use the Fail Counter and the Pass Counter in order to determine how the number of ignition cycles in which the diagnostic reported a pass and/or a fail. Operate the vehicle within the same Freeze Frame conditions that the PCM recorded, including the RPM, the load, the vehicle speed, and the temperature. This procedure isolates when the DTC failed.
If the scan tool indicates that the HO2S voltage goes below 200 mV, this indicates the HO2S circuits and PCM are OK.
This step verifies whether the low signal circuit from the PCM is OK. A voltage indicates that the PCM and the wiring are OK.
This step verifies whether the signal circuit from the PCM is OK.
Disconnecting the PCM allows you to use a DMM in order to test the circuit continuity. This procedure helps to locate an open or shorted circuit.
Step
Action
Values
Yes
No
Schematic Reference: Engine Controls Schematics
1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Important
Inspect the HO2S for being secure before proceeding with this DTC. A loose sensor could cause this DTC to set.
Install a scan tool.
Start the engine and idle the engine at the normal operating temperature.
Operate the engine above 1200 RPM for 2 minutes.
Observe the HO2S voltage with a scan tool.
Does the HO2S voltage vary outside the specified range?
350-550 mV
Go to Step 3
Go to Step 4
3
Observe the Freeze Frame and/or Failure Records data for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame and/or Failure Records data that you observed.
Does the DTC fail this ignition?
--
Go to Step 4
Go to Intermittent Conditions
4
Turn ON the ignition, with the engine OFF.
Disconnect the HO2S.
Jumper the HO2S high signal circuit to a known good ground.
Jumper the HO2S low signal circuit to a known good ground.
Observe the HO2S voltage with a scan tool.
Is the HO2S voltage below the specified value?
200 mV
Go to Step 8
Go to Step 5
5
Remove both jumper wires.
Use the DMM in order to measure the voltage from the HO2S low signal circuit to a battery ground.
Is the voltage near the specified value?
5V
Go to Step 6
Go to Step 7
6
Turn OFF the ignition.
Disconnect the PCM connector C1. Refer to Powertrain Control Module (PCM) Replacement .
Test for continuity of the HO2S high signal circuit. Refer to Testing for Continuity in Wiring Systems.
If no continuity is indicated on the DMM, repair the open circuit. Refer to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 10
7
Turn OFF the ignition.
Disconnect the PCM connector C1. Refer to Powertrain Control Module (PCM) Replacement .
Test for continuity of the HO2S low signal circuit. Refer to Testing for Continuity in Wiring Systems.
If no continuity is indicated on the DMM, repair the open or the faulty connection Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 10
8
Inspect the HO2S circuits for a faulty connection at the HO2S harness connector. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.
If you find a faulty connection, replace or repair the terminal as necessary. Refer to Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 9
9
Replace the affected HO2S. Refer to Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 2 .
Did you complete the replacement?
--
Go to Step 12
--
10
Inspect the HO2S circuits for a faulty connection at the PCM. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.
If you find a faulty connection, replace or repair the terminal as necessary. Refer to Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 11
11
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?
--
Go to Step 12
--
12
Use a scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?
--
Go to Step 13
Go to Step 2
13
With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List
System OK
DTC P1220
Circuit Description
The throttle position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. Two separate signal, low reference and 5-volt reference circuits are used in order to connect the TP sensor assembly to the throttle actuator control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage is pulled up to the reference voltage as the throttle opens, from below 1 volt at closed throttle to above 3.5 volts at wide open throttle (WOT). The TP sensor 2 signal voltage is pulled down to the low reference from around 3.8 volts at closed throttle to below 1 volt at WOT. TP sensor 1 and APP sensor 1 share a 5-volt reference circuit that is connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that is connected within the TAC module. If an out of range condition is detected with the TP sensor 2, this DTC will set and the Reduced Engine Power message will be displayed.
Conditions for Running the DTC
DTCs P1517, or P1518 are not set.
The ignition switch in the crank position or run the position.
The ignition voltage is greater than 5.23 volts.
Conditions for Setting the DTC
The TP sensor 2 voltage is less than 0.13 volts or greater than 4.87 volts.
All above conditions present for less than 1 second.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Inspect the throttle actuator control (TAC) module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing.
When the TAC module detects a condition within the TAC System, more than one TAC System related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
If this DTC is determined to be intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Using a test lamp reduces the amount of current fed into the signal circuit. The scan tool should display the maximum value for this parameter, 5-volts even though the actual voltage is higher.
The TP 2 sensor and the APP 2 sensor share a common 5 volt reference. The 5-volt reference circuits are connected internally within the TAC module. Disconnecting the TAC module will isolate the 5-volt reference circuits.
The TP sensor 2 and the APP sensor 2 share a common 5-volt reference. A short to voltage on the APP sensor 2, 5-volt reference circuit will affect the TP sensor 2, 5-volt reference circuit.
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This condition is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
DTC P1220 - Throttle Position (TP) Sensor 2 Circuit Step
Action
Values
Yes
No
Schematic Reference: Engine Controls Schematics
1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Is DTC P1515, P1516, or P1518 also set?
--
Go to Diagnostic Trouble Code (DTC) List
Go to Step 3
3
Turn OFF the ignition.
Remove the air inlet duct from the throttle body assembly.
Disconnect the throttle actuator motor harness connector.
Turn ON the ignition, with the engine OFF.
Manually close the throttle blade completely while observing the TP sensor 2 voltage parameter on the scan tool.
Does the scan tool indicate that the TP sensor 2 voltage is within the specified values?
4.3-4.8 V
Go to Step 4
Go to Step 7
4
Open the throttle blade to wide open throttle (WOT) by hand while observing the TP sensor 2 voltage parameter on the scan tool.
Does the scan tool indicate TP sensor 2 voltage within the specified values?
0.13-1 V
Go to Step 5
Go to Step 7
5
Turn OFF the ignition for 15 seconds.
Reconnect the throttle actuator motor harness connector.
Reinstall the air inlet duct.
Turn ON the ignition with the engine OFF.
Select the DTC Info. option on the scan tool.
Lightly touch and move the related engine wiring harnesses and connectors for the TP sensor while observing the DTC Info. The DTC will set if an intermittent condition is present. Refer to Testing for Intermittent and Poor Connections and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 6
6
Continue to observe DTC Info.
Slowly depress the accelerator pedal to WOT and then slowly return the pedal to the released position 3 times.
Does the scan tool indicate this DTC failed this ignition?
--
Go to Step 26
Go to Diagnostic Aids
7
With a scan tool, observe the TP sensor 2 voltage parameter.
Does the scan tool indicate that the TP sensor 2 voltage is at the specified value?
5 V
Go to Step 8
Go to Step 12
8
Disconnect the TP sensor harness connector.
Does the scan tool indicate that the TP sensor 2 voltage is at the specified value?
0 V
Go to Step 9
Go to Step 13
9
Disconnect the APP sensor harness connector.
Turn ON the ignition with the engine OFF.
With a DMM, test the TP sensor 2, 5-volt reference circuit for voltage.
Does the DMM indicate voltage near the specified value?
5 V
Go to Step 10
Go to Step 18
10
With a DMM connected between the TP sensor 1 low reference circuit and the TP sensor 2 low reference circuit at the TP sensor harness connector, test for resistance
Does the DMM indicate resistance within the specified values?
0-5 ohms
Go to Step 14
Go to Step 11
11
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the TP sensor circuits.
With a DMM, test the TP sensor 2 low reference circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 32
12
Disconnect the TP sensor harness connector.
Connect a test lamp between the TP sensor 2 signal circuit and the battery positive voltage.
Does the scan tool indicate TP sensor 2 voltage near the specified value?
5 V
Go to Step 20
Go to Step 15
13
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the TP sensor circuits.
Turn ON the ignition.
With a DMM, test the TP sensor 2 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 17
14
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the APP sensor circuits.
Turn ON the ignition with the engine OFF.
With a DMM, test the APP sensor 2 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 24
15
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the TP sensor circuits.
With a DMM, test the TP sensor 2 signal circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 16
16
With a DMM, test the TP sensor 2 signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 17
17
With a DMM, test for a short between the TP sensor 2 signal circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 32
18
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the TP sensor circuits.
Turn ON the ignition with the engine OFF.
With a DMM, test the TP sensor 2, 5-volt reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 19
19
Turn OFF the ignition.
Disconnect the other TAC module harness connector.
Turn ON the ignition with the engine OFF.
With a DMM, test the APP sensor 2 5-volt reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 24
20
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the TP sensor circuits.
With a DMM, test the TP sensor 2 5-volt reference circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 21
21
With a DMM, test the TP sensor 2 5-volt reference circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 22
22
Disconnect the APP sensor harness connector.
Disconnect the other TAC module harness connector.
Turn ON the ignition with the engine OFF.
With a DMM, test the APP sensor 2 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 23
23
With a DMM, test the APP sensor 2 5-volt reference circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 24
24
With a DMM, test the TP sensor 2 5-volt reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 25
25
With a DMM, test for a short between the TP sensor 2 5-volt reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 26
26
With a DMM, test for a short between the APP sensor 2 5-volt reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 27
27
With a DMM, test the TP sensor 2 signal circuit for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 28
28
With a DMM, test the TP sensor 2 low reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 29
29
Reconnect the TAC module connectors.
Turn ON the ignition.
With a DMM, measure voltage at the TP sensor 2, 5-volt reference circuit.
Does the DMM indicate voltage greater than the specified value?
6.06 V
Go to Step 32
Go to Step 30
30
Turn OFF the ignition.
Connect a test lamp between APP sensor 2, 5-volt reference and battery positive voltage.
Does the test lamp illuminate?
--
Go to Step 32
Go to Step 31
31
Inspect for poor connections at the TP sensor harness connector. Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 33
32
Inspect for poor connections at the TAC module harness connector. Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 35
Go to Step 34
33
Important
The throttle position sensor is not a serviceable part and should only be replaced with the throttle body assembly.
Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .
Did you complete the replacement?
--
Go to Step 35
--
34
Replace the TAC module. Refer to Throttle Actuator Control (TAC) Module Replacement .
Did you complete the replacement?
--
Go to Step 35
--
35
Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?
--
Go to Step 36
Go to Step 2
36
With a scan tool, observe the stored information, Capture Info.
Does the scan tool indicate any DTCs that you have not diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List
System OK
DTC P1221
Circuit Description
The throttle position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. Two separate signal, low reference and 5 volt reference circuits are used in order to connect the TP sensor assembly to the throttle actuator control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage is pulled up to the reference voltage as the throttle opens, from below 1 volt at closed throttle to above 3.5 volts at wide open throttle (WOT). The TP sensor 2 signal voltage is pulled down to the low reference from around 3.8 volts at closed throttle to below 1 volt at WOT. TP sensor 1 and APP sensor 1 share a 5-volt reference circuit that is connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that is connected within the TAC module. If an out of range condition is detected with the TP sensors, this DTC will set and the Reduced Engine Power message will be displayed.
Conditions for Running the DTC
DTCs P1517, or P1518 are not set.
The ignition switch is in the crank or run position.
The ignition voltage is greater than 5.23 volts.
Conditions for Setting the DTC
TP sensor 2 disagrees with TP sensor 1 by more than 7.5 percent.
All above conditions are present for less than 1 second.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing.
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
If this DTC is determined to be intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
DTC P1221 - Throttle Position (TP) Sensors 1, 2 Performance Step
Action
Yes
No
Schematic Reference: Engine Controls Schematics
1
Did you perform the Diagnostic System Check-Engine Controls?
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Is DTC P1518 also set?
Go to Diagnostic Trouble Code (DTC) List
Go to Step 3
3
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the TP sensor 1 and 2 Agree/Disagree parameter.
Does the scan tool TP sensor 1 and 2 Agree/Disagree parameter indicate Disagree?
Go to Step 5
Go to Step 4
4
Remove the air inlet duct from the throttle body.
Disconnect the throttle actuator motor harness connector.
Slowly manually open the throttle blade to WOT and back to the closed throttle position several times while observing the scan tool TP sensor Agree/Disagree parameter.
Does the TP sensor Agree/Disagree parameter change from Agree to Disagree during the above test?
Go to Step 18
Go to Step 5
5
Disconnect the TP sensor harness connector.
Disconnect the TAC module harness connectors.
Test the TP sensor 1 5-volt reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 6
6
With a DMM, test for a short between the TP sensor 1 5-volt reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 7
7
With a DMM, test the TP sensor 1 signal circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 8
8
With a DMM, test for a short between the TP sensor 1 signal circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 9
9
With a DMM, test the TP sensor 1 low reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 10
10
With a DMM, test for a short between the TP sensor 1 low reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 11
11
With a DMM, test the TP sensor 2 5-volt reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 12
12
With a DMM, test for a short between the TP sensor 2 5-volt reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 13
13
With a DMM, test the TP sensor 2 signal circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 14
14
With a DMM, test for a short between the TP sensor 2 signal circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 15
15
With a DMM, test the TP sensor 2 low reference circuit for resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 16
16
With a DMM, test for a short between the TP sensor 2 low reference circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 17
17
Inspect for poor connections at the harness connector of the TAC module. Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 18
18
Inspect for poor connections at the harness connector of the TP sensor. Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?
Go to Step 20
Go to Step 19
19
Important
The throttle position sensor is not a serviceable part and should only be replaced with the throttle body assembly.
Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .
Did you complete the replacement?
Go to Step 20
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20
Use a scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?
Go to Step 21
Go to Step 2
21
With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?
Go to Diagnostic Trouble Code (DTC) List
System OK
Bill
