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 more than 4.75 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.
An intermittent may be caused by the following:
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 0 APP operation. Scan APP 1 sensor while depressing the accelerator pedal with the engine and the ignition ON. Display should vary from about 0.74 volt when the throttle is closed to about 3.7 volts when the throttle is held at wide open throttle (WOT). A P0123 will result if the ground circuit is open or the signal circuit is shorted to voltage.
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 Testing for Electrical Intermittents in Wiring Systems.
If a repair is necessary, then refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Values | 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 modules data is deleted once the Clear Info function is used. Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Is the APP 1 above the specified value? | 4.75 V | |||
3 | The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored, refer to the applicable DTC tables first. Are any additional DTCs stored? | -- | Go to applicable DTC | Go to Diagnostic Aids |
4 |
Is the APP 1 less than the specified value? | 0.25 V | ||
5 | Probe the APP 1 sensor ground circuit at the APP sensor harness connector with an unpowered test lamp connected to B+. Is the test lamp ON? | -- | ||
6 |
Was the APP 1 sensor signal circuit shorted? | -- | ||
7 | Check for proper electrical connections at the APP sensor and replace the terminals if necessary. Refer to Wiring Repairs in Wiring Systems. Did any terminals require replacement? | -- | ||
8 |
Was the APP 1 sensor ground circuit open? | -- | ||
9 | Replace the APP module. Refer to Accelerator Pedal Position Module Replacement . Is the action complete? | -- | -- | |
10 |
Important: The new PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | |
11 |
Does the scan tool indicate the diagnostic Passed? | -- | ||
12 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to applicable DTC | System OK |
