GM Service Manual Online
For 1990-2009 cars only

Object Number: 550686  Size: MF
Engine Controls Components
Cruise Control, APP Module
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The accelerator pedal position (APP) module provides a voltage signal that changes relative to the accelerator pedal position. There are 3 sensors which are located within the APP module that are scaled differently.

Conditions for Running the DTC

    • The ignition voltage is more than 6.4 volts.
    • The engine speed is more than 300 RPM.
    • There are no in range faults for APP 1 or APP 2--The PCM checks for high and low voltage faults.

Conditions for Setting the DTC

    • The difference between APP 3 and APP 1 is more than 0.23 volts--The PCM compares the pre-scaled voltage that is internal to the PCM.
    • The difference between APP 3 and APP 2 is more than 0.50 volt--The PCM compares the pre-scaled voltage that is internal to the PCM.
    • The conditions are met for 2 seconds.

Action Taken When the DTC Sets

    •  The service throttle soon lamp will not illuminate when one APP DTC sets. The PCM will only illuminate the service throttle soon lamp when multiple APP DTCs set.
    • The powertrain control module (PCM) records the operating conditions at the time the diagnostic fails. This information is stored in the Failure Records.

Conditions for Clearing the MIL/DTC

    • A History DTC clears after 40 consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
    • Use a scan tool in order to clear the DTCs.

Diagnostic Aids

There are no driveability issues associated with the APP module unless a DTC is present. The most likely causes of this DTC are faulty connections or the sensor itself. The least cause likely is a PCM problem.

An intermittent may be caused by:

    • Faulty connections
    • Rubbed-through wire insulation
    • A broken wire inside the insulation

A scan tool reads the APP 3 position in volts. The scan tool should read approximately 4.0 volts with the throttle closed and the ignition ON or at idle. The voltage should decrease at a steady rate as the throttle is moved toward a wide open throttle (WOT). Also, 90 percent pedal travel is acceptable for correct APP operation. Scan the APP 3 sensor while depressing the accelerator pedal with the engine stopped and the ignition ON. The display should vary from approximately 4.0 volts when the throttle was closed to approximately 2.0 volts when the throttle is held at the WOT position.

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

  1. This step determines if there is a good reference voltage.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing any DTCs, use the scan tool Capture Info function in order to save the Freeze Frame and the Failure records for reference. The control module's data is deleted once the Clear Info function is used.

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Turn ON the ignition, with the engine OFF.
  2. With the throttle closed, observe the APP voltages on the scan tool.

Are the APP voltages at the specified values? The values are listed as APP 1, APP 2, and APP 3 respectively.

0.45-0.95 V

4.0-4.5 V

3.6-4.0 V

Go to Step 3

Go to Step 4

3

The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If any additional DTCs are stored, refer to the applicable DTC tables first.

Are any additional DTCs stored?

--

Go to the applicable DTC table

Go to Diagnostic Aids

4

  1. Disconnect the APP sensor electrical connector.
  2. Turn ON the ignition, with the engine OFF.
  3. With a J 39200 DMM connected to ground, probe the APP sensor 5-volt reference circuits at the APP harness terminals.

Is the voltage more than or equal to the specified value on all of the circuits?

4.75 V

Go to Step 5

Go to Step 6

5

  1. Turn ON the ignition, with the engine OFF.
  2. With a J 35616-200 unpowered test lamp connected to B+, probe the APP sensor ground circuits at the APP sensor harness terminals.

Is the test lamp ON for all of the circuits?

--

Go to Step 9

Go to Step 8

6

  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Check the 5-volt reference circuit for an open or short to ground.
  4. If the 5-volt reference circuit is open or shorted to ground, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

--

Go to Step 11

Go to Step 7

7

Check the 5-volt reference circuit for a faulty connection at the PCM and replace the terminal if necessary. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

--

Go to Step 11

Go to Step 10

8

  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Check for an open sensor ground circuit to the PCM.
  4. If you find a problem, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

--

Go to Step 11

Go to Step 10

9

Replace the APP module. Refer to Accelerator Pedal Position Module Replacement .

Is the action complete?

--

Go to Step 11

--

10

Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Is the action complete?

--

Go to Step 11

--

11

  1. Use a scan tool in order clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the normal operating temperature is reached.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number that was set.
  6. Operate the vehicle within the Conditions for Setting this DTC until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

--

Go to Step 12

Go to Step 2

12

Does the scan tool display any additional undiagnosed DTCs?

--

Go to the applicable DTC table

System OK