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 control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
A scan tool reads the APP 1 position in volts. The APP 1 position should read approximately 0.45-0.95 volts with the throttle closed and the ignition ON or at idle. The 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 the 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 WOT position. A DTC 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 powertrain control module (PCM) and the wiring.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 |
Important: Before clearing any DTCs, use the scan tool Capture Info in order to save the Freeze Frame/Failure Records for reference. The scan tool loses data when the Clear Info function is used. Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Is the APP 1 display more than the specified value at a closed throttle? | 4.75 V | Go to Step 4 | Go to Step 3 | |
The DTC is intermittent. Are there any additional DTCs stored? | -- | Go to Diagnostic Aids | ||
4 |
Is the APP 1 less than the specified value? | 0.25 V | Go to Step 5 | Go to Step 6 |
5 | Probe the APP 1 sensor ground circuit at the APP sensor harness connector with a test light connected to B+. Does the test light illuminate? | -- | Go to Step 7 | Go to Step 8 |
6 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
7 |
Did you find and correct the condition? | -- | Go to Step 12 | -- |
8 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
9 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 |
10 | Replace the APP module. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the scan tool indicate the diagnostic passed? | -- | Go to Step 13 | Go to Step 2 |
13 | Does the scan tool display any additional undiagnosed DTCs? | -- | System OK | |
