P2127
DTC P2120, P2122, P2123, P2125, 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 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
Typical Scan Tool Data
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 each sensor with a signal circuit, 5 V reference circuit, and a low reference circuit.
Conditions for Running DTC
P2120, P2122, P2123, P2125, P2127, P2128
* DTC P0641 or P0651 is not set.
* The run/crank or powertrain relay voltage is greater than 6 V and reduced power is not active.
* The ignition is ON or the engine is operating.
* DTC P0120, P0122, P0123, P0220, P0222, P0223, and P2135 run continuously when the above conditions are met.
P2138
* DTC P0641, P0651, P2120, P2122, P2123, P2125, P2127 or P2128 are not set.
* The ignition is ON or the engine is operating.
* The run/crank or powertrain relay voltage is greater than 6 V and reduced power is not active.
* DTC P2138 runs continuously when the above conditions are met.
Conditions for Setting DTC
P2120
The ECM detects that the APP sensor 1 voltage is less than 0.463 V or greater than 4.75 V for less than 1 s.
P2122
The ECM detects that the APP sensor 1 voltage is less than 0.463 V for less than 1 s.
P2123
The ECM detects that the APP sensor 1 voltage is greater than 4.75 V for less than 1 s.
P2125
The ECM detects that the APP sensor 2 voltage is less than 0.325 V or greater than 2.6 V for less than 1 s.
P2127
The ECM detects that the APP sensor 2 voltage is less than or equal to 0.325 V for less than 1 s.
P2128
The ECM detects that the APP sensor 2 voltage is greater than 2.6 V for less than 1 s.
* The ECM detects that APP sensor 1 and APP sensor 2 disagree greater than 10 percent for less than 1 s.
Or
* The ECM detects that both APP sensor 1 and APP sensor 2 are 5 percent greater than the learned minimum position for less than 1 s.
Action Taken When the DTC Sets
* DTCs P2120, P2122, P2123, P2125, 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 P2120, P2122, P2123, P2125, 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.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
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 (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify DTC P0641 or P0651 are not set.
• If a DTC is set, refer to DTC P0641 or P0651 (P0641) for further diagnosis.
2. Observe the scan tool APP sensor 1 and 2 voltage parameters. The reading should be between 0.46-4.75 V for APP 1 and 0.325-4.75 V for APP 2, and change with accelerator pedal input.
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. Clear the DTCs with the scan tool. Operate the vehicle within the Conditions for Running the DTC or within the conditions that you observed from the Freeze Frame/Failure Records.
5. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P2120 or P2125 are not the only APP sensor DTCs set.
• If DTC P2120 or P2125 are the only DTCs set, replace the ECM.
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 B107 accelerator pedal. Allow at least 60 s for the ECM to power down. This can be verified by a loss of communication message on the scan tool.
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 D
* APP sensor 2 terminal A
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit/connections test normal, replace the K20 ECM.
3. Ignition ON, test for 4.8-5.2 V between the appropriate 5-volt reference circuit terminal listed below and ground.
* APP sensor 1 terminal F
* APP sensor 2 terminal C
• If less than the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit/connections 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 circuit/connections test normal, replace the ECM.
4. Verify the scan tool APP sensor 1 and 2 voltages are less than 0.2 V.
• If greater than the specified range, test the APP sensor 1 and 2 signal circuits terminals B or E for a short to voltage. If the circuit tests normal, replace the K20 ECM.
5. Install a 3 A fused jumper wire between the APP sensor 1 signal circuit terminal E and the 5-volt reference circuit terminal F. 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 K20 ECM.
6. Install a 3 A fused jumper wire between the APP sensor 2 signal circuit terminal B and the 5-volt reference circuit terminal F. 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 K20 ECM.
7. If all circuits/connections test normal, test or replace the B107 Accelerator Pedal Position Sensor.
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 (Programming and Relearning) for ECM replacement, setup, and programming