Heavy Duty L96
DTC P2122, P2123, P2127, P2128, or P2138 (Heavy Duty L96)
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)provide 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 V reference circuit, a low reference circuit, and a signal circuit.
Conditions for Running the DTC
P2122, P2123, P2127, P2128
* DTC P0697 or P06A3 is not set.
* The ignition is ON or the engine is running.
* The run/crank or powertrain relay voltage is greater than 6.4 V and reduced power is not active.
* DTC P2122, P2123, P2127, P2128 run continuously when the above conditions are met.
P2138
* DTC P2122, P2123, P2127, P2128, P0697, or P06A3 are not set.
* The ignition is ON or the engine is running.
* The run/crank or powertrain relay voltage is greater than 6.4 V and reduced power is not active.
* 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 0.46 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 0.32 V for greater than 0.2 s.
P2128
The ECM detects that the APP sensor 2 voltage is greater than 2.6 V for greater than 0.2 s.
P2138
The voltage difference between APP sensor 1 and APP sensor 2 exceeds a predetermined value for greater than 1 s.
Action Taken When the DTC Sets
* DTCs P2122, P2123, P2127, P2128, and P2138 are Type A DTCs.
* 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
DTCs P2122, P2123, P2127, P2128, and P2138 are Type A DTCs.
Diagnostic Aids
A high resistance condition on the accelerator pedal sensor 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 (except L96) ([1][2]Electrical Diagrams)Engine Controls Schematics (L96) ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Throttle Actuator Control (TAC) System Description (Throttle Actuator Control (TAC) System Description)
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 (Control Module References)for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P0697 or P06A3 are not set.
• If a DTC is set, refer to DTC P0641, P0651, P0697, or P06A3 (ECM, L96) (P0641) for further diagnosis.
2. Observe the scan tool APP Sensor 1 voltage parameter. Verify APP sensor 1 voltage is between 0.46-4.75 V and changes with accelerator pedal input.
3. Observe the scan tool APP Sensor 2 voltage parameter. Verify APP sensor 2 voltage is between 0.32-2.6 V and changes with accelerator pedal input.
4. 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.
5. Observe the DTC information with a scan tool. DTCs P2122, P2123, P2127, P2128, or P2138 should not set.
6. 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, disconnect the harness connector at the Accelerator Pedal 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 terminal listed below and ground.
* APP sensor 1 terminal F
* APP sensor 2 terminal A
• If greater than the specified range, disconnect the ECM and test the low reference circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.
3. Ignition ON, test for 4.8-5.2 V between the appropriate 5 V reference circuit terminal 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 open/high resistance. If the circuit/connections test normal, replace the ECM.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.
4. Verify the scan tool APP sensor 1 voltage is less than 0.3 V.
• If greater than the specified range, disconnect the ECM and test the signal circuit terminal E for a short to voltage. If the circuit/connections test normal, replace the ECM.
5. Verify the scan tool APP sensor 2 voltage is less than 0.3 V.
• If greater than the specified range, disconnect the ECM and test the signal circuit terminal B for a short to voltage. If the circuit/connections test normal, replace the ECM.
6. Connect a 3 A fused jumper wire between the APP sensor 1 signal circuit terminal E and the 5 V reference circuit terminal D. Verify the APP sensor 1 voltage parameter is greater than 4.8 V.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.
7. Connect a 3 A fused jumper wire between the APP sensor 2 signal circuit terminal B and the 5 V reference circuit terminal D. Verify the APP sensor 2 voltage parameter is greater than 4.8 V.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.
8. If all circuits/connections 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)
* Control Module References (Control Module References)for Engine Control Module replacement, programming, and setup