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 voltage is more than 6.4 volts. |
| • | The engine speed is more than 300 RPM. |
| • | There are no in range faults for the APP 2 sensor or the APP 3 sensor (PCM checks for high and low voltage faults). |
Conditions for Setting the DTC
| • | The difference between the APP 1 sensor and the APP 2 sensor is more than 0.23 volts (PCM compares pre-scaled voltage (internal to PCM)). |
| • | The difference between the APP 1 sensor and the APP 3 sensor is more than 0.50 volts (PCM compares pre-scaled voltage (internal to PCM)). |
| • | 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 is stored 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:
| • | Poor connections |
| • | Rubbed through wire insulation |
| • | Broken wire inside the insulation |
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 1 sensor while depressing accelerator pedal with the engine off and the ignition ON. Display should vary from about 0.74 volt when the throttle is closed to over about 3.7 volts when the throttle is held at wide open throttle (WOT). The following chart will check voltages on all APP circuits to see if they fall in normal ranges. The PCM compares pre-scaled voltages (these are voltages that the scan tool cannot read). The scan tool reads only output voltages.
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.
-
This step determines if there is a good 5 volt reference.
-
This step will check for an open in the ground circuit.
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? | -- | ||
2 |
Are APP voltages at specified values (values listed are APP 1, APP 2, and APP 3 respectively)? | 0.45-0.95 V 4.0-4.5 V 3.6-4.1 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 |
Is the voltage more than or equal to the specified value on all circuits? | 4.75 V | |||
Is the test lamp ON (all circuits)? | -- | |||
6 |
Was the 5 volt reference circuit open or shorted to ground? | -- | ||
7 | Check the 5 volt reference 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? | -- | ||
8 |
Was APP 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 |
