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VIN L




DTC P2122, P2123, P2127, P2128, or P2138

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

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

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

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





Typical Scan Tool Data









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.

The engine control module (ECM) uses the APP sensors input to determine the amount of fuel to deliver for acceleration or deceleration that is desired.

Conditions for Running the DTC

P2122, P2123, P2127, and P2128
* The ignition is ON or the engine is running.
* DTCs P2122, P2123, P2127, and P2128 run continuously when the above conditions are met.

P2138
* DTCs P2122, P2123, P2127, and P2128 is not set.
* The ignition is ON or the engine is running.
* DTC P2138 runs continuously when the above conditions are met.

Conditions for Setting the DTC

P2122

The ECM detects that the APP sensor 1 voltage is less than 0.8 V for greater than 0.2 s.

P2123

The ECM detects that the APP sensor 1 voltage is greater than 4.75 V for greater than 0.2 s.

P2127

The ECM detects that the APP sensor 2 voltage is less than 0.3 V for greater than 0.2 s.

P2128

The ECM detects that the APP sensor 2 voltage is greater than 2.3 V for greater than 0.2 s.

P2138

The ECM detects that APP sensor 1 and APP sensor 2 disagree greater than 2 percent for greater than 0.2 s.

Action Taken When the DTC Sets

* DTCs P2122, P2123, P2127, P2128, and P2138 are Type C DTCs.
* The driver information center, if equipped, may display Reduced Engine Power message.
* The engine speed is increased.
* Diesel particulate filter (DPF) regeneration is inhibited.

Conditions for Clearing the DTC

DTCs P2122, P2123, P2127, P2128, and P2138 are Type C DTCs.

Diagnostic Aids

* A high resistance condition on the accelerator pedal position circuits could cause a DTC to set.
* Ensure that the in-line harness connector seals are installed correctly. Improper installation could result in water intrusion into the connector and cause a DTC to set.

Reference Information
Schematic Reference

Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify DTCs P0651 or P0697 are not set.

• If a DTC is set, refer to DTC P0641, P0651, P0697, P06A3, P06D2, or P06D6 (P0641) for further diagnosis.

2. Observe the appropriate APP sensor circuit status parameter listed below with a scan tool. Each parameter should display OK.

* APP Sensor 1 Circuit Status
* APP Sensor 2 Circuit Status

3. Observe the scan tool APP Sensor 1 and 2 Agree/Disagree parameter while performing the following tests:

* Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times.
* Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times.
The APP Sensor 1 and 2 Agree/Disagree parameter should display Agree.

4. Verify the scan tool APP Sensor 1 voltage parameter is between 0.80-4.75 V and changes with accelerator pedal input.
5. Verify the scan tool APP Sensor 2 voltage parameter is between 0.30-2.30 V and changes with accelerator pedal input.
6. Operate the vehicle within the Conditions for Running the DTC to verify that 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, disconnect the harness connector at the APP sensor assembly.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohm between the appropriate low reference circuit listed below and ground:

* APP sensor 1 terminal F
* APP sensor 2 terminal A

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit test normal, replace the K20 ECM.

3. Ignition ON, test for 4.8-5.2 V between the appropriate 5 V reference circuit listed below and ground:

* APP sensor 1 terminal D
* APP sensor 2 terminal C

• If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the K20 ECM.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.

4. Verify the scan tool APP Sensor 1 and APP Sensor 2 parameters are less than 0.2 V.

• If greater than the specified range, test the appropriate signal circuit terminals listed below for a short to voltage. If the circuit tests normal, replace the K20 ECM.

* APP sensor 1 terminal E
* APP sensor 2 terminal B

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

* APP sensor 1 terminal E
* APP sensor 2 terminal B

• 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 K20 ECM.

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

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Accelerator Pedal Position Sensor Replacement (Service and Repair)
* Perform the scan tool Diesel Particulate Filter (DPF) Regeneration Enable (Diesel Particulate Filter (DPF) Regeneration Enable) procedure if the scan tool DPF Soot Mass is less than 30 g. If the scan tool DPF Soot Mass is 30 g or greater, perform the Diesel Particulate Filter (DPF) Service Regeneration (Diesel Particulate Filter (DPF) Service Regeneration) procedure.
* Control Module References (Programming and Relearning) for ECM replacement, programming, and setup

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