Hi, I have a 2002 C5 and I'm having problems. Most I have fixed but I'm having trouble passing smog and the check engine light keeps coming on. The code I'm getting is p1285, 1286. I have replaced the APP sensor and cleared the codes but two days later they reappeared. Is there another part of the fly by wire system I should be checking, please any help is welcome help,.
Thanks

 

Did I mention the car has never idled rough.. Bogged.. Stuttered.. Nothing. It's been my everyday driver since 2004. The new sensor did nothing, changed nothing in the way it runs. It's kinda upsetting to think only the second time I've had to smog the car and it's already failing. Im not getting TAC module codes or any other codes for that matter... Just these two and only these two. Im looking for a direction or any other person who has heard anything similar..

 

You may have a throttle actuator control (TAC) module laying down on you, below is the troubleshooting guide

Cheers,
Kevin

For the 2002 C5 Codes P1285/1286
--------------------------------------------------------------------------------

DTC P1285
Circuit Description
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is actually 3 individual APP sensors within 1 housing. Three separate signal, low reference and 5-volt reference circuits connect the APP sensor assembly and the throttle actuator control (TAC) module. Each sensor has a unique functionality. The APP sensor 1 signal increases as the accelerator pedal is depressed, from below 1 volt at 0 percent pedal travel, with the pedal at rest, to above 2 volts at 100 percent pedal travel, with the pedal fully depressed. The APP sensor 2 signal decreases from above 4 volts at 0 percent pedal travel to below 2.9 volts at 100 percent pedal travel. The APP sensor 3 signal decreases from around 3.8 volts at 0 percent pedal travel to below 3.1 volts at 100 percent pedal travel. Notice that the signal circuits for APP sensor 2 and APP sensor 3 pull up to 5-volts and the APP sensor 1 signal circuit is referenced to low reference within the TAC module.

Conditions for Running the DTC
• DTCs P0606, P1517, or P1518 are not set.

• The ignition switch is in the crank or the run position.

• The ignition voltage is greater than 5.23 volts.

Conditions for Setting the DTC
• APP sensor 3 voltage is less than 01.63 volts or greater than 4.28 volts.

• All above conditions present for less than 1 second.

Action Taken When the DTC Sets
• The control module stores the DTC information into memory when the diagnostic runs and fails.

• The malfunction indicator lamp (MIL) will not illuminate.

• The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

• If one or more APP sensor DTCs are set for a single APP sensor, the following occurs:

- The control module will not command Reduced Engine Power mode.

- The control module will use the remaining two APP sensors to calculate throttle response.

• If certain multiple APP sensor DTCs are set for more than one APP sensor, the following occurs:

- The control module commands Reduced Engine Power mode.

- The APP indicated angle is limited to a predetermined value to limit the amount of throttle control.

- The message center displays Reduced Engine Power.

• If all three APP sensors are out of range, the following occurs:

- The control module commands Reduced Engine Power mode.

- The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle.

- The message center displays Reduced Engine Power.

Conditions for Clearing the DTC
• 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 non-emission related diagnostic.

• Clear 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 throttle movement with a DTC P1285 set, a DTC P1286 also sets.

• 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.

• For an intermittent, refer to Intermittent Conditions .

Test Description
The number below refers to the step number 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 the components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.

DTC P1285 - Accelerator Pedal Position (APP) Sensor 3 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: If DTC P1518 or P1220 is also set, refer to Diagnostic Trouble Code (DTC) List for further diagnosis.

Turn ON the ignition, with the engine OFF.
With a scan tool, observe the APP senso 3 voltage parameter.
Does the scan tool indicate APP sensor 3 voltage within the specified values?
3.29-4.28 V
Go to Step 3
Go to Step 6

3
Fully depress the accelerator pedal to the wide open throttle (WOT) position.

Does the scan tool indicate APP sensor 3 voltage within the specified values?
1.63-3.1 V
Go to Step 4
Go to Step 6

4
Turn OFF the ignition for 15 seconds.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the diagnostic trouble code (DTC) option.
Lightly touch and move the related engine wiring harnesses and connectors for the APP sensor while monitoring the DTC info status.
Did this DTC fail this ignition during the above test?
--
Go to Step 20
Go to Step 5

5
Slowly depress the accelerator pedal to WOT. Slowly return the accelerator pedal to the released position.

Did this DTC fail this ignition during the above test?
--
Go to Step 21
Go to Diagnostic Aids

6
Disconnect the APP sensor harness connector.
With a DMM, Test the APP sensor 3 signal circuit for voltage.
Does the DMM indicate APP sensor 3 signal voltage within the specified values?
3.94-6.06 V
Go to Step 11
Go to Step 7

7
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 3 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 25
Go to Step 8

8
With a DMM, test the APP sensor 3 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 25
Go to Step 9

9
With a DMM, test the APP sensor 3 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 25
Go to Step 10

10
Disconnect the other TAC module harness connector.
With a DMM, test for a short between the APP sensor 3 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 25
Go to Step 23

11
With a DMM, test the APP sensor 3 5-volt reference circuit for voltage.

Does the DMM indicate voltage within the specified values?
3.94-6.06 V
Go to Step 16
Go to Step 12

12
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 3 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 25
Go to Step 13

13
With a DMM, test the APP sensor 3 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 25
Go to Step 14

14
With a DMM, test the APP sensor 3 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 25
Go to Step 15

15
With a DMM, test for a short between the APP sensor 3 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 25
Go to Step 23

16
With a DMM connected between the APP sensor 3 low reference circuit and the APP sensor 1 low reference circuit, measure the resistance.

Does the DMM indicate resistance within the specified values?
0-5 ohms
Go to Step 18
Go to Step 17

17
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the APP sensor circuits.
With a DMM, test the APP sensor 3 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 25
Go to Step 23

18
With a scan tool , observe the APP sensor 3 voltage parameter.
Connect a fused jumper between the APP sensor 3 signal circuit and the APP sensor 3 low reference circuit at the APP sensor harness connector.
Does the scan tool indicate APP sensor 3 voltage at the specified value?
0 V
Go to Step 19
Go to Step 24

19
Turn OFF the ignition.
Disconnect the TAC module harness connectors.
With a DMM, test for a short between the APP sensor 3 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 25
Go to Step 21

20
Repair the intermittent connection as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?
--
Go to Step 25
--

21
Inspect for poor connections at the harness connector of the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 25
Go to Step 22

22
Replace the APP sensor assembly. Refer to Accelerator Pedal Position Sensor Replacement .

Did you complete the replacement?
--
Go to Step 25
--

23
Inspect for poor connections at the harness connector of the TAC module . Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 25
Go to Step 24

24
Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement .

Did you complete the replacement?
--
Go to Step 25
--

25
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 26
Go to Step 2

26
With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

DTC P1286
Circuit Description
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is actually 3 individual APP sensors within 1 housing. Three separate signal, low reference and 5-volt reference circuits connect the APP sensor assembly and the throttle actuator control (TAC) module. Each sensor has a unique functionality. The APP sensor 1 signal increases as the accelerator pedal is depressed, from below 1 volt at 0 percent pedal travel, with the pedal at rest, to above 2 volts at 100 percent pedal travel, with the pedal fully depressed. The APP sensor 2 signal decreases from above 4 volts at 0 percent pedal travel to below 2.9 volts at 100 percent pedal travel. The APP sensor 3 signal decreases from around 3.8 volts at 0 percent pedal travel to below 3.1 volts at 100 percent pedal travel. Notice that the signal circuits for APP sensor 2 and APP sensor 3 pull up to 5-volts and the APP sensor 1 signal circuit is referenced to low reference within the TAC module.

Conditions for Running the DTC
• DTCs P0606, 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
• APP sensor 3 disagrees with APP sensor 1 by more than 13 percent and APP sensor 3 disagrees with APP sensor 2 by more than 13 percent.

• All of the above conditions are present for less than 1 second.

Action Taken When the DTC Sets
• The control module stores the DTC information into memory when the diagnostic runs and fails.

• The malfunction indicator lamp (MIL) will not illuminate.

• The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

• If one or more APP sensor DTCs are set for a single APP sensor, the following occurs:

- The control module will not command Reduced Engine Power mode.

- The control module will use the remaining two APP sensors to calculate throttle response.

• If certain multiple APP sensor DTCs are set for more than one APP sensor, the following occurs:

- The control module commands Reduced Engine Power mode.

- The APP indicated angle is limited to a predetermined value to limit the amount of throttle control.

- The message center displays Reduced Engine Power.

• If all three APP sensors are out of range, the following occurs:

- The control module commands Reduced Engine Power mode.

- The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle.

- The message center displays Reduced Engine Power.

Conditions for Clearing the DTC
• 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 non-emission related diagnostic.

• Clear 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 throttle movement with a DTC P1285 set, a DTC P1286 also sets.

• 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.

• For an intermittent, refer to Intermittent Conditions .

Test description
The numbers below refer to the step numbers in the diagnostic table.

This step determines if a communication condition exists.

This step isolates an internal APP sensor failure. The condition may only occur at a certain accelerator pedal position. Monitoring the APP angles for sensor 1 and sensor 2 is an accurate way of verifying the actual position of the pedal. The APP angles for all 3 sensors should be within a few percent of each other. When the pedal is at rest, the APP angle for all 3 sensors should be 0 percent. When the pedal is fully depressed, all APP angles should be 100 percent.

The APP sensor 3 has a dedicated 5-volt reference circuit. Monitoring the APP sensor 1 voltage aids in diagnosing the APP sensor 3 5-volt reference circuit. If the scan tool displays 5 volts then the circuits are OK.

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 P1286 APP Sensor 3 Performance 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 P1518 also set?
--
Go to DTC P1518
Go to Step 3

3
Important: Do not depress the accelerator pedal.

Turn OFF the ignition for 15 seconds.
Start the engine.
With a scan tool, observe the DTC info.
Did any other TAC module or APP sensor DTCs set except DTC P1125?
--
Go to Diagnostic Trouble Code (DTC) List
Go to Step 4

4
With a scan tool, observe the APP sensor Agree/Disagree parameters.

Does the scan tool indicate Disagree for any of the APP sensor Agree/Disagree parameters?
--
Go to Step 6
Go to Step 5

5
Turn ON the ignition, with the engine OFF.
With a scan tool. observe the APP sensor angles for all 3 APP sensors.
Slowly depress the accelerator pedal, stopping at 25, 50, 75, and 99 percent.
Slowly release the accelerator pedal, stopping at 75, 50, 25, and 0 percent.
Does the scan tool indicate that the APP sensor 3 angle is within 13 percent of both APP sensors 1 and 2 angles?
--
Go to Diagnostic Aids
Go to Step 6

6
Turn off the ignition.
Disconnect the APP sensor harness connector.
With a DMM, test the APP sensor 3 5-volt reference circuit for voltage.
Does the DMM indicate voltage within the specified values
3.94-6.06 V
Go to Step 7
Go to Step 14

7
With a DMM, test the APP sensor 3 signal circuit for voltage.

Does the DMM indicate voltage within the specified values
3.94-6.06 V
Go to Step 8
Go to Step 16

8
With a DMM connected between the APP sensor 3 low reference circuit and the APP sensor 1 low reference circuit, measure the resistance.

Does the DMM indicate resistance within the specified values?
0-5 ohms
Go to Step 9
Go to Step 19

9
Disconnect the TAC module harness connector containing the APP sensor circuits.
With a DMM, test the APP sensor 3 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 24
Go to Step 10

10
With a DMM, test for a short between the APP sensor 3 5-volt reference circuit and all other APP circuits at the APP sensor harness connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 24
Go to Step 11

11
With a DMM, test the APP sensor 3 signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 24
Go to Step 12

12
With a DMM, test for a short between the APP sensor 3 signal circuit and all other APP circuits at the APP sensor harness connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 24
Go to Step 13

13
With a DMM, test the APP sensor 3 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 24
Go to Step 20

14
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the APP sensor circuits.
With a DMM, test the APP sensor 3 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 24
Go to Step 15

15
With a DMM, test the APP sensor 3 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 24
Go to Step 21

16
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the APP sensor circuits.
With a DMM, test the APP sensor 3 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 24
Go to Step 17

17
With a DMM, test the APP sensor 3 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 24
Go to Step 18

18
With a DMM, test for a short between the APP sensor 3 signal circuit and all other APP circuits at the APP sensor harness connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 24
Go to Step 19

19
Turn OFF the ignition.
Disconnect the TAC module harness connector containing the APP sensor circuits.
With a DMM, test the APP sensor 3 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 24
Go to Step 21

20
Inspect for poor connections at the harness connector of the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 24
Go to Step 22

21
Inspect for poor connections at the harness connectors of the TAC module. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 24
Go to Step 23

22
Replace the APP sensor assembly. Refer to Accelerator Pedal Position Sensor Replacement .

Did you complete the replacement?
--
Go to Step 24
--

23
Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement .

Did you complete the replacement?
--
Go to Step 24
--

24
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 25
Go to Step 2

25
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