bmfrc

I just got my 2nd c5 about 3 months ago, a 99 with a 402 bottom end, ls3 heads and intake, I think ls3 throttle body, and I am not sure about what the maf is. For the most part, it runs great, but when I come to a stop, the rpms will hang around 2k until you rev it to 5k or so, then it will settle to a normal idle. It also will surge from a normal idle to around 1700 rpm when I come to a stop, like you are just tapping on the pedal.. I've gotten 2 pcm codes: 0101 and 0507. I checked all of the connections and they appear fine. I was having some voltage problems, and replaced the battery, but this problem stuck around. Any ideas before I start tearing into this beast???

lucky131969

Please post ALL codes.

Bill Curlee

DTC P0101
Circuit Description
The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The powertrain control module (PCM) uses the MAF sensor signal in order to provide the correct fuel delivery for a wide range of engine speeds and engine loads. A small quantity of air entering the engine indicates a deceleration or an idle. A large quantity of air entering the engine indicates an acceleration or a high load situation. The MAF sensor has an ignition 1 voltage circuit, a ground circuit and a signal circuit. The PCM applies a voltage to the sensor on the signal circuit. The sensor uses the voltage in order to produce a frequency based on the inlet air flow through the sensor bore. The PCM uses the manifold absolute pressure (MAP), the intake air temperature (IAT) and the engine RPM in order to calculate a predicted MAF value. The PCM compares the actual MAF sensor signal to the predicted MAF value in order to determine if the signal is stuck based on a lack of variation, or is too low or too high for a given operating condition. DTC P0101 will set if the actual MAF sensor signal is not within a predetermined range of the calculated MAF value.

Conditions for Running the DTC
DTCs P0102, P0103, P0106, P0107, P0108, P1120, P1220, or P1221 are not set.
The engine is running.
The ignition 1 signal is at least 11 volts and no more than 18 volts.
The throttle position (TP) indicated angle is less than 95 percent.
The TP indicated angle is steady within a range of less than 5 percent.
The manifold absolute pressure (MAP) sensor is less than 80 kPa.
The MAP sensor is steady within a range of less than 3 kPa.
All of the above conditions are present for greater than 2 seconds.
Conditions for Setting the DTC
The actual MAF sensor signal is not within a predetermined range of the calculated MAF value.
The above condition is present for greater than 8 seconds.
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
Inspect for the following conditions:

A misrouted harness--Inspect the MAF sensor harness in order to ensure that the harness is not routed too close to the following sensors or components:
The ignition coils
Any solenoids
Any relays
Any motors
Excessive deposits on the throttle plate or in the throttle bore
Any unmetered air entering the engine may cause this DTC to set--Verify that the oil dipstick is fully seated and that the oil fill cap is secure.
A wide-open throttle (WOT) acceleration from a stop should cause the MAF sensor value to increase. This increase of about 4-7 gm/s at idle to 190 gm/s or more will display on a scan tool at the time of the 1-2 shift. If this increase does not occur, inspect for a restriction.
A skewed MAP sensor will cause the calculated mass air flow value to be inaccurate. The value shown for the MAP sensor display varies with the altitude. With the ignition ON and the engine OFF, 103 kPa is the approximate value displayed at, or near sea level. The value decreases by approximately 3.0 kPa for every 305 m (1,000 feet) of altitude.
If you suspect that the vehicle condition may be related to aftermarket accessories, refer to Checking Aftermarket Accessories in Wiring Systems.

If the problem is intermittent, refer to Intermittent Conditions .

Test Description
The numbers below refer to the step numbers on the diagnostic table.

Before using this table, diagnose any MAF, MAP, TP, or system voltage DTCs. If a misfire condition exists or if a rough running condition is observed with or without the DTC P0300, proceed to DTC P0300.

Any unmetered air which enters the engine may cause this DTC to set. This step eliminates any conditions which can cause a DTC to set with a normally operating MAF sensor.

This step verifies the signal circuit from the MAF sensor electrical connector to the PCM. A voltage reading of less than 4 volts or greater than 6 volts indicates a malfunction in the wiring or a faulty connection.

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
Install a scan tool.
Start the engine.
Use a scan tool in order to monitor the diagnostic trouble code (DTC) Information.
Does the scan tool display any other DTCs set?
--
Go to Diagnostic Trouble Code (DTC) List
Go to Step 3

3
Observe and record the Freeze Frame/Failure Records for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
In order to operate the vehicle under the conditions which set the DTC, use the following information:
The data in the Freeze Frame/Failure Records
The parameters listed in the Conditions for Running in the DTC
Does the DTC fail this ignition?
--
Go to Step 4
Go to Diagnostic Aids

4
Start and idle the engine.
With a scan tool observe the MAP sensor voltage parameter.
Does the scan tool indicate that the MAP sensor voltage is within the specified range?
0.8-4.0 V
Go to Step 5
Go to DTC P0106

5
Turn OFF the ignition.
Inspect for the following conditions:
Objects blocking the MAF sensor air inlet screen
A plugged or collapsed intake air duct or a dirty air filter element
Inspect for vacuum leaks in the following components:
The intake manifold
The throttle body
The MAF sensor seal
The MAP sensor seal
The EVAP purge solenoid seal
Components in the crankcase ventilation system
Components in the brake booster system
Components in the air induction system
Did you find and correct the condition?
--
Go to Step 22
Go to Step 6

6
Remove the MAP sensor from the engine vacuum source, with the electrical harness connected. Refer to Manifold Absolute Pressure (MAP) Sensor Replacement .
Connect a hand operated vacuum pump to the MAP sensor.
Turn ON the ignition, with the engine OFF.
With a scan tool observe or record the kPa parameter display of the MAP sensor. SLOWLY apply vacuum 1 inch Hg at a time. Increment the vacuum up to 20 inches Hg which is indicated on the pump gauge. Each inch of vacuum applied should result in a 3-4 kPa drop in the MAP sensor value on the scan tool. The value should change smoothly with each inch increase in vacuum.
Does the scan tool indicate that the MAP sensor value changed smoothly through the entire range of the test?
--
Go to Step 7
Go to DTC P0106

7
Apply 20 inches Hg vacuum to the MAP sensor.

Does the scan tool indicate that the MAP sensor reading is equal to or less than the specified value?
34 kPa
Go to Step 8
Go to DTC P0106

8
Disconnect the vacuum source from the MAP sensor.

Does the scan tool indicate that the MAP sensor reading returned to the original value that was observed in step 6?
--
Go to Step 9
Go to DTC P0106

9
Turn OFF the ignition.
Disconnect the MAF sensor harness connector.
Turn ON the ignition, with the engine OFF.
Measure the voltage from the signal circuit of the MAF sensor to a good ground. Refer to Circuit Testing in Wiring Systems.
Does the voltage measure near the specified value?
5 V
Go to Step 10
Go to Step 11

10
Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and the ground circuit of the MAF sensor. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?
--
Go to Step 18
Go to Step 13

11
Does the voltage measure less than the specified value?
4.5 V
Go to Step 14
Go to Step 12

12
Turn OFF the ignition.

important
Disconnecting the PCM connectors may eliminate the short to voltage if the signal circuit is shorted to another PCM circuit. Refer to Circuit Testing in Wiring Systems.


Disconnect the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Turn ON the ignition, with the engine OFF.
Measure the voltage from the signal circuit of the MAF sensor to a good ground.
Does the voltage measure near the specified value?
0 V
Go to Step 21
Go to Step 17

13
Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?
--
Go to Step 15
Go to Step 16

14
Turn OFF the ignition.
Disconnect the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Test the signal circuit between the PCM and the MAF sensor for the following conditions:
A high resistance or an open
A short to ground
A short to the ground circuit of the MAF sensor--Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 22
Go to Step 19

15
Repair the high resistance or an open in the ground circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?
--
Go to Step 22
--

16
Repair the short to ground or an open in the Ignition 1 voltage circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems.
Replace the fuse if necessary.
Did you complete the repair?
--
Go to Step 22
Go to Step 20

17
Repair the short to voltage in the signal circuit of the MAF sensor. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?
--
Go to Step 22
--

18
Inspect for faulty connections at the harness connector of the MAF sensor. Refer to Testing for Intermittent and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 22
Go to Step 20

19
Inspect for faulty connections at the harness connector of the PCM. Refer to Testing for Intermittent and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 22
Go to Step 21

20
Replace the MAF sensor. Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement .

Did you complete the replacement?
--
Go to Step 22
--

21
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .

Did you complete the replacement?
--
Go to Step 22
--

22
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 23
Go to Step 2

23
With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not been diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List
System OK



--------------------------------------------------------------------------------
Document ID# 671571
2001 Chevrolet/Geo Corvette



DTC P0507
Circuit Description
The electronic throttle control system uses various inputs from the powertrain control module (PCM). This system uses these inputs in order to control the idle speed through serial data circuits to the throttle actuator control (TAC) module. The DC motor, which is located on the throttle body, activates the throttle plate. In order to decrease idle speed, the TAC module commands the throttle closed reducing the air flow into the engine and decreasing the idle speed. In order to increase the idle speed, the TAC module commands the throttle plate open, allowing more air to bypass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC will set.

Conditions for Running the DTC
DTCs P0101-P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0171, P0172, P0174, P0175, P0200, P0300, P0440, P0442, P0443, P0500, P0502, P0503, P1120, P1220, P1221, or P1441 are not set.
The engine is running for greater than 60 seconds.
The engine coolant temperature (ECT) is greater than 60°C (140°F).
The intake air temperature (IAT) is greater than -10°C (+14°F).
The BARO is greater than 65 kPa.
The system voltage is between 9-18 volts.
The vehicle speed is less than 1.7 km/h (1 mph).
The accelerator pedal position (APP) sensor is at 0 percent.
Conditions for Setting the DTC
The actual idle speed is 200 RPM greater than the desired idle speed.
All of the above conditions present for 5 seconds.
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.
Test Description
The number below refers to the step number on the diagnostic table.

This test determines if the engine can achieve the commanded RPM.

Step
Action
Yes
No

1
Did you perform the Diagnostic System Check-Engine Controls?
Go to Step 2
Go to Diagnostic System Check - Engine Controls

2
Set the park brake, and block the drive wheels.
Start the engine.
Turn OFF all accessories.
With the RPM control function of the scan tool, command the engine RPM to 1,500 RPM, then to 500 RPM, and back to 1,500 RPM.
Did the engine speed stay within 200 RPM of the commanded RPM during the above test?
Go to Step 3
Go to Step 4

3
Observe the Freeze Frame/Failure Records for this DTC.
Turn OFF the ignition for 30 seconds.
In order to operate the vehicle under the conditions which set the DTC, use the following information:
The data in the Freeze Frame/Failure Records
The parameters listed in the Conditions for Running in the DTC
Does the DTC set?
Go to Step 4
Go to Intermittent Conditions

4
Inspect for the following conditions:

Deposits in the throttle body
A faulty PCV valve
Did you find and complete the repair?
Go to Step 5
--

5
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 6
Go to Step 2

6
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



--------------------------------------------------------------------------------
Document ID# 703664
2001 Chevrolet/Geo Corvette

bmfrc

Turns out the mass air flow is fine! The intake is a stock ls3 that has been heavily modded, and has a leak on the bottom of it!!! Time to find a FAST 102!!