For 1990-2009 cars

### Circuit Description

The accelerator pedal position (APP) sensors 1 and 2 are located within the accelerator pedal assembly. Each sensor has the following circuits:

• | A 5-volt reference circuit

• | A low reference circuit

• | A signal circuit

This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2138 Accelerator Pedal Position (APP) Sensor 1-2 Correlation

### Conditions for Running the DTC

• | The battery voltage is more than 5.23 volts.

• | DTCs P0641, P0651, P2120, P2125 are not set.

• | The accelerator pedal is leaving the idle position.

• | DTC P2138 runs continuously when the above conditions are met.

### Conditions for Setting the DTC

The voltage difference between APP sensor 1 and APP sensor 2 exceeds a predetermined value for more than 2 seconds.

### Action Taken When the DTC Sets

• | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.

• | The control module commands the TAC system to operate in the Reduced Engine Power mode.

• | A message center or an indicator displays Reduced Engine Power.

• | Under certain conditions the control module commands the engine OFF.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive drive trips that the diagnostic runs and does not fail.

• | A History DTC clears after 40 consecutive warm up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.

• | The scan tool clears the MIL/DTC.

### Diagnostic Aids

The PCM compares the signal of each of the accelerator pedal position sensor to each other throughout the entire range of operation. Clear the DTCs and actuate the pedal through the entire range with the ignition ON and the engine OFF.

Use the J 35616 Connector Test Adapter Kit for any test that requires probing the PCM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.

For intermittent conditions, refer to Intermittent Conditions .

### Test Description

The number below refers to the step number on the diagnostic table.

1. Any circuit faults on either APP sensor 1 or 2 will set one of the DTCs listed. Refer to the appropriate table for diagnosis.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Observe the DTC information with a scan tool. Is DTC P0120, P0220, P0641, P0651, P2120, or P2125 also set? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | Go to Step 3
3 |

1. Turn OFF the ignition.
2. Disconnect the accelerator pedal position (APP) sensor electrical connector.
3. Disconnect the powertrain control module (PCM).
4. Use a DMM to measure the resistance of the following circuits for each of the APP sensors:

• | The low reference circuit

• | The signal circuit

• | The 5-volt reference circuit

Did any of the circuits measure more than the specified value?

5 Ohms

Go to Step 5

Go to Step 4

4 |

1. Test for a short between any of the circuits in the APP sensor harness.
2. Repair the circuit as necessary. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 7

Go to Step 6

5 | Repair the high resistance in the circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 7 | --
6 | Replace the APP sensor. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 7 | --
7 |

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze/Frame Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 8

8 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK