Diagnostic Instructions

DTC Descriptors

DTC P2120: Accelerator Pedal Position (APP) Sensor 1 Circuit

DTC P2122: Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage

DTC P2123: Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage

DTC P2125: Accelerator Pedal Position (APP) Sensor 2 Circuit

DTC P2127: Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage

DTC P2128: Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage

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

Diagnostic Fault Information

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
APP Sensor 1 Signal	P2122	P2138	P2122	P2123	P2120, P2138
APP Sensor 1 5-Volt Reference	P0335, P0651, P2122, P2138	P2138	P2122	P2123, P2138, P0651	P2120, P2138
APP Sensor 1 Low Reference	--	P2138	P2123	--	P2120, P2138
APP Sensor 2 Signal	P2127	P2138	P2127	P2128	P2120, P2138
APP Sensor 2 5-Volt Reference	P0641, P2127, P2138	P2138	P2127	P2128, P0641	P2120, P2138
APP Sensor 2 Low Reference	--	P2138	P2128	--	P2120, P2135

Typical Scan Tool Data

APP Sensor 1

Circuit	Short to Ground	Open	Short to Voltage
Parameter Normal Range: APP 1 varies 1.02-4.29 V
APP Sensor 1 Signal	0 V	0 V	4.98 V
APP Sensor 1 5-Volt Reference	0 V	0 V	4.98 V
APP Sensor 1 Low Reference	--	5 V	--

APP Sensor 2

Circuit	Short to Ground	Open	Short to Voltage
Parameter Normal Range: APP 2 varies 0.50-2.50 V
APP Sensor 2 Signal	0 V	0 V	4.98 V
APP Sensor 2 5-Volt Reference	0 V	0 V	4.98 V
APP Sensor 2 Low Reference	--	4.98 V	--

Circuit/System Description

The accelerator pedal assembly contains 2 accelerator pedal position (APP) sensors. The APP sensors are mounted to the accelerator pedal assembly and are not serviceable. The APP sensors provide a signal voltage that changes relative to pedal position. The engine control module (ECM) supplies each APP sensor with a 5-volt reference circuit, a low reference circuit, and a signal circuit.

Conditions for Running DTC

P2120, P2122, P2123, P2125, P2127, P2128

P2138

Conditions for Setting DTC

P2120 and P2125

The ECM detects the APP sensor voltage is less than 0.33 volts or greater than 4.5 volts for less than 1 second.

P2122 and P2127

The ECM detects the APP sensor voltage is less than 0.33 volts for less than 1 second.

P2123 and P2128

The ECM detects the APP sensor voltage is greater than 4.5 volts for less than 1 second.

P2138

The ECM detects the voltage difference between APP sensor 1, and APP sensor 2, exceeds a value of 5 percent with the pedal in the released position, or 10 percent with the pedal at wide open throttle (WOT) for less than 1 second.

Action Taken When the DTC Sets

Conditions for Clearing the MIL/DTC

DTCs P2120, P2122, P2123, P2125, P2127, P2128, and P2138 are type A DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

ADD LINK

Scan Tool Reference

Engine Control Module Scan Tool Information

Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify DTCs P0641 or P0651 is not set.

⇒	If either DTC is set, refer to DTC P0641 or P0651 for further diagnosis.

2. Ignition ON, observe the scan tool APP sensor 1, and APP sensors 2 voltage parameters. The parameters should display between 0.5-4.5 volts, and change with accelerator pedal input.
3. Observe the scan tool APP sensors 1 and 2 parameter while operating the accelerator pedal from the rest position to wide open throttle (WOT). The scan tool should indicate agree through the entire range.
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 data.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the accelerator pedal.
2. Test for less than 5 ohms between the following low reference circuit terminals and ground:

•	APP Sensor 1 terminal D

•	APP Sensor 2 terminal A

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

3. Ignition ON, test for 4.8-5.8 volts between the following 5-volt reference circuit terminals and ground:

•	APP Sensor 1 terminal F

•	APP Sensor 2 terminal C

⇒	If less than the specified range, test the appropriate 5-volt reference circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.

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

4. Verify the following scan tool parameters:

•	APP Sensor 1 less than 1 volt

•	APP Sensor 2 greater than 4 volts

⇒	If less than the specified range, test the appropriate signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

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

5. Install a 3A fused jumper wire between APP sensor 1 signal circuit terminal E and the 5-volt reference circuit terminal F. Verify the scan tool APP sensor 1 voltage parameter is greater than 4.5 volts.

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

6. Install a 3A fused jumper wire between APP sensor 2 signal circuit terminal B and ground. Verify the scan tool APP sensor 2 voltage parameter is less than 0.5 volts.

⇒	If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.