For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P2120: Accelerator Pedal Position (APP) Sensor 1 Circuit Malfunction
DTC P2125 03: Accelerator Pedal Position (APP) Sensor 2 Circuit Voltage Below Threshold
DTC P2125 07: Accelerator Pedal Position (APP) Sensor 2 Circuit Voltage Above Threshold
DTC P2138 5A: Accelerator Pedal Position (APP) Sensor 1-2 Correlation Plausibility Failure

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
Accelerator Pedal Position (APP) Sensor 1 5-Volt Reference Circuit | P0641 | P2138 | P2120 | P0641 | --
Accelerator Pedal Position (APP) Sensor 2 5-Volt Reference Circuit | P0651 | P2138 | P2125 | P0651, P0190 | --
Accelerator Pedal Position (APP) Sensor 1 Signal | P2120 | P2138 | P2120 | P0641, P2120 | P2138
Accelerator Pedal Position (APP) Sensor 2 Signal | P2125 | P2138 | P2125 | P2125 | P2138
Accelerator Pedal Position (APP) Sensor 1 Low Reference | -- | P2138 | P2120 | -- | --
Accelerator Pedal Position (APP) Sensor 1 Low Reference | -- | P2138 | P2125 | -- | --

### Typical Scan Tool Data

#### APP Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The engine is operating at idle. Parameter Normal Range: APP Sensor 1 0.9-1.2 Volts Parameter Normal Range: APP Sensor 2 varies 0.45-0.62 Volts
5-Volt Reference 1 | 0 Volts | 0 Volts | APP 1 2.08 Volts
5-Volt Reference 2 | 0 Volts | 0 Volts | APP 2 0.86 Volts
APP Sensor 1 Signal | 0 Volts | 0 Volts | 5 Volts
APP Sensor 2 Signal | 0 Volts | 0 Volts | 5 Volts
APP Sensor 1 Low Reference | -- | 5 Volts | --
APP Sensor 2 Low Reference | -- | 5 Volts | --

### Circuit/System Description

The accelerator pedal assembly contains two accelerator pedal position (APP) sensors. The APP sensors are mounted in the pedal assembly and are not serviceable. The APP sensors provide a signal voltage that changes relative to the position of the accelerator pedal. The engine control module (ECM) supplies a separate 5-volt reference and low reference circuit for each of the APP sensors.

The APP sensor 1 signal voltage increases as the pedal is depressed, from approximately 1 volt at rest to above 4 volts when fully depressed. The APP sensor 2 signal voltage increases as the pedal is depressed, from approximately 0.5 volts at rest to greater than 2 volts with the accelerator pedal fully depressed.

### Conditions for Running the DTCs

• | The ignition is ON or the engine is operating.

• | The DTCs run continuously once the above conditions are met.

### Conditions for Setting the DTC

#### P2120 03

The APP sensor 1 voltage is out of range for greater than 4 seconds.

#### P2120 07

The APP sensor 1 voltage is greater than 4.62 volts for greater than 4 seconds.

#### P2125 03

The APP sensor 2 voltage is less than 0.28 volts for greater than 4 seconds.

#### P2125 07

The APP sensor 2 voltage is greater than 2.32 volts for greater than 4 seconds.

#### P2138 5A

The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than a predetermined value.

### Action Taken When the DTC Sets

DTCs P2120, P2125, and P2138 are Type C DTCs.

### Conditions for Clearing the DTC

DTCs P2120, P2125, and P2138 are Type C DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

1. Ignition ON, observe the scan tool APP Sensor parameters. Both readings should be between 0.4-1.5 V.
2. Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times. DTCs P2120, P2125, or P2138 should not set.
3. Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times. DTCs P2120, P2125, or P2138 should not set.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, and the MAIN fuse removed, disconnect the harness connector at the B107 accelerator pedal assembly.
2. Test for less than 5 Ω between the appropriate low reference circuit and ground.

• | APP Sensor 1 low reference circuit terminal 4

• | APP Sensor 2 low reference circuit terminal 2

⇒ | If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuits test normal, replace the K20 ECM.

Note: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.

3. Install the MAIN fuse. Ignition ON, test for 4.8-5.2 V between the appropriate 5-volt reference circuit and ground.

• | APP Sensor 1 5-volt reference circuit terminal 5

• | APP Sensor 2 5-volt reference circuit terminal 6

⇒ | If less the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuits test normal, replace the K20 ECM.

⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuits test normal, replace the K20 ECM.

4. Verify both scan tool APP sensor parameters are less than 0.3 V.

⇒ | If greater than the specified range, test the appropriate signal circuit for a short to voltage. If the circuits test normal, replace the K20 ECM.

5. Install a 3 A fused jumper wire between the appropriate signal circuit and the 5-volt reference circuit. Verify the scan tool APP sensor parameter is greater than 4.8 V.

• | APP Sensor 1 signal circuit terminal 3

• | APP Sensor 2 signal circuit terminal 1

⇒ | If less than the specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K20 ECM.

⇒ | If both scan tool APP sensor parameters display greater than the specified range, test the signal circuits for a shorted together condition. If the circuits test normal, replace the K20 ECM.

6. If all circuits test normal, replace the B107 accelerator pedal assembly.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Accelerator Pedal Position Sensor Replacement

• | Control Module References for engine control module replacement, setup, and programming