GM Service Manual Online
For 1990-2009 cars only

Object Number: 185076  Size: LF
Engine Controls Components
EGR, MAF and Accelerator Pedal Controls
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 accelerator pedal position. There are three sensors located within the APP module that are scaled differently.

Conditions for Running the DTC

    • The PCM performs this DTC diagnostic continuously.
    • The ignition switch in the ON position.

Conditions for Setting the DTC

    • The voltage on the APP 1 sensor is less than 0.25 volts.
    • All of the diagnostic set conditions 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 PCM records the operating conditions at the time the diagnostic fails. This information will store in the Failure Records.

Conditions for Clearing the MIL/DTC

    • A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures
    • The use of a scan tool.

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 poor connections or the sensor itself. The least likely is a PCM problem.

A scan tool reads APP 1 position in volts. It should read about 0.45 to 0.95 volt with the throttle closed and the ignition ON or at idle. Voltage should increase at a steady rate as the throttle is moved toward wide open throttle (WOT). Also, 90 percent pedal travel is acceptable for correct APP operation. Scan APP sensor while depressing the accelerator pedal with the engine off and the ignition ON. Display should vary from about 0.74 volt when throttle is closed to about 3.7 volts when the throttle is held at wide open throttle (WOT). A DTC P0122 will result if the signal or reference circuit are open.

An intermittent may be caused by any of the following conditions:

    • A poor connection
    • Rubbed through wire insulation
    • A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

  1. This step determines if P0122 is the result of a hard failure or an intermittent condition.

  2. This step checks the PCM and wiring.

Step

Action

Value(s)

Yes

No

1

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

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

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

Is the APP 1 voltage less than or equal to the specified value?

0.25 V

Go to Step 4

Go to Step 3

3

The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored, refer to those table(s) 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. Jumper the APP 1 signal circuit and the 5 volt reference circuit together at the APP sensor harness connector.
  3. Observe the APP 1 voltage on the scan tool.

Is the APP 1 voltage greater than the specified value?

4.75 V

Go to Step 10

Go to Step 5

5

  1. Connect an J 35616-200 unpowered test lamp between B+ and the APP 1 sensor signal circuit at the APP sensor harness connector.
  2. Observe the APP 1 voltage on the scan tool.

Is the APP 1 voltage greater than the specified value?

4.75 V

Go to Step 6

Go to Step 8

6

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

Was the 5 volt reference circuit open or shorted to ground?

--

Go to Step 12

Go to Step 7

7

Check the 5 volt reference circuit for a proper 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 13

Go to Step 12

8

  1. Turn the ignition OFF.
  2. Disconnect the PCM, and check the APP 1 signal circuit for an open, or a short to ground.
  3. If the APP 1 sensor signal circuit is open or shorted to ground, repair it as necessary. Refer to Wiring Repairs in Wiring Systems.

Was the APP 1 signal circuit open or shorted to ground?

--

Go to Step 13

Go to Step 9

9

Check the APP 1 sensor signal circuit for a proper connection at the PCM and replace terminal if necessary. Refer to Wiring Repairs in Wiring Systems.

Did the terminal require replacement?

--

Go to Step 13

Go to Step 12

10

Check for a proper electrical connection at the APP module. Repair the connection if necessary. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

--

Go to Step 13

Go to Step 11

11

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

Is the action complete?

--

Go to Step 13

--

12

Replace the PCM.

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

Is the action complete?

--

Go to Step 13

--

13

  1. Using the scan tool, clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches normal operating temperature.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number which was set.
  6. Operate the vehicle, with 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 14

Go to Step 2

14

Does the scan tool display any additional undiagnosed DTCs?

--

Go to the Applicable DTC Table

System OK