Diagnostic Instructions

DTC Descriptors

DTC P2120 03: Accelerator Pedal Position (APP) Sensor 1 Circuit Voltage Below Threshold

DTC P2120 07: Accelerator Pedal Position (APP) Sensor 1 Circuit Voltage Above Threshold

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 more than 2 volts with the accelerator pedal fully depressed.

Conditions for Running the DTCs

Conditions for Setting the DTC

P2120 03

The APP sensor 1 voltage is less than 0.59 volts for more than 4 seconds.

P2120 07

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

P2125 03

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

P2125 07

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

P2138 5A

The ECM detects that the voltage difference between APP sensor 1 and 2 is more 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

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Circuit/System Verification

1. Ignition ON, observe the scan tool APP Sensor parameters. Verify both of the readings are between 0.4-1.5 volts.
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. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing

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

⇒	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 ECM.

Important: 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 volts between the appropriate 5-volt reference circuit and ground.

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

⇒	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 ECM.

4. Verify the appropriate scan tool APP sensor parameter is less than 0.3 volt.

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

5. Install a 3A 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 volts.

⇒	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 ECM.

⇒	If both scan tool APP sensor parameters display greater than 4.8 volts, test the signal circuits for being shorted together condition. If the circuits test normal, replace the ECM.

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.