Circuit Description
The Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to the accelerator pedal position. There are 3 sensors located within the APP module that are scaled differently.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | The voltage is more than 4.75 volts on the APP 1 sensor. |
| • | The condition was 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 stores in the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | A History DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other emissions related diagnostic. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
A scan tool reads the APP 1 position in volts. It should read approximately 0.45--0.95 volts 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% pedal travel is acceptable for correct APP operation. Scan APP 1 sensor while depressing the accelerator pedal with the engine stopped and the ignition ON. The display should vary from approximately 0.74 volts when the throttle is closed to approximately 3.7 volts when the throttle is held at the Wide Open Throttle (WOT) position. A P0123 will result if the ground circuit is open or if the signal circuit is shorted to voltage.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
-
This step determines if DTC P0123 is the result of a hard failure or an intermittent condition.
-
This step checks the PCM and the wiring.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing any DTCs, use the Scan Tool Capture Info in order to save the Freeze Frame and Failure Records for reference. The Scan Tool loses data when the Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Is the APP 1 display more than the specified value at a closed throttle? | 4.75V | |||
The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If any additional DTCs were stored, refer to the applicable DTC tables first. Are there any additional DTCs stored? | -- | Go to the applicable DTC table | Go to Diagnostic Aids | |
4 |
Is the APP 1 less than the specified value? | 0.25V | ||
5 | Probe the APP 1 sensor ground circuit at the APP sensor harness connector with a test light connected to B+. Is the test light ON? | -- | ||
6 |
Was a repair performed? | -- | ||
7 |
Is action complete? | -- | -- | |
8 |
Was a repair performed? | -- | ||
9 |
Was a repair performed? | -- | ||
10 | Replace the APP module. Refer to Accelerator Pedal Position Module Replacement . Is the action complete? | -- | -- | |
11 |
Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | |
12 |
Does the Scan Tool indicate the diagnostic Passed? | -- | ||
13 | Does the Scan Tool display any additional undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK |
