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P2138




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 00
- Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage

DTC P2123 00
- Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage

DTC P2127 00
- Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage

DTC P2128 00
- Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage

DTC P2138 00
- Accelerator Pedal Position (APP) Sensors 1-2 Not Plausible

Diagnostic Fault Information





Typical Scan Tool Data










Circuit/System Description

The throttle actuator control (TAC) system uses two accelerator pedal position (APP) sensors to monitor the accelerator pedal position. The APP sensors 1 and 2 are located within the pedal assembly. Each sensor has a 5 V reference circuit, a low reference circuit, and a signal circuit.

Two processors are also used to monitor the TAC motor system data. Both processors are located within the engine control module (ECM). Each signal circuit provides both processors with a signal voltage proportional to pedal movement. The processors share and monitor data to verify that the indicated APP sensor calculation is correct.

Conditions for Running the DTC

P2122 00, P2123 00, P2127 00, P2128 00
* The system voltage is greater than 7 V.
* The ignition is in the unlock, accessory, run, or crank position.
* DTC P0642 00, P0643 00, or P0606 00 is not set.
* The DTCs run continuously when the above conditions are met.

P2138 00
* The system voltage is greater than 7 V.
* The ignition is in the unlock, accessory or run position.
* DTC P0642 00, P0643 00, P0606 00, P2122 00, P2123 00, P2127 00, or P2128 00 is not set.
* The DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

P2122 00

The ECM detects that APP sensor 1 voltage is less than 0.63 V for greater than 0.5 s.

P2123 00

The ECM detects that APP sensor 1 voltage is greater than 4.588 V for greater than 0.5 s.

P2127 00

The ECM detects that APP sensor 2 voltage is less than 0.12 V for greater than 0.5 s.

P2128 00

The ECM detects that APP sensor 2 voltage is greater than 2.64 V for greater than 0.5 s.

P2138 00

The ECM detects that the difference between APP sensor 1 and APP sensor 2 exceeds a predetermined value for greater than 2 s.

Action Taken When the DTC Sets

* DTCs P2122 00, P2123 00, P2127 00, P2128 00 and P2138 00 are Type A DTCs.
* The ECM commands the TAC motor system to operate in reduced engine power mode.

Conditions for Clearing the DTC

DTCs P2122 00, P2123 00, P2127 00, P2128 00, and P2138 00 are Type A DTCs.

Reference Information
Schematic Reference

Engine Controls Schematics ([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 (Programming and Relearning)

Circuit/System Verification

1. Ignition ON, observe the scan tool APP Sensor 1 Position parameter. The reading should be between 0.313-4.87 V, and change with the accelerator pedal input.
2. Ignition ON, observe the scan tool APP Sensor 2 Position parameter. The reading should be between 0.16-2.30 V, and change with the accelerator pedal input.
3. Clear the DTCs with the scan tool.
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.
5. Verify that the following DTCs are not set: DTC P0642 00, P0643 00.

• If DTCs P0642 00, P0643 00 are set, refer to DTC P0642, P0643, P0652, or P0653 (P0642).

Circuit/System Testing

1. Ignition OFF for 90 s, disconnect the harness connector at the B107 Accelerator Pedal Position Sensor.
2. Test for less than 3 ohm between each of the B107 Accelerator Pedal Position Sensor low reference circuit terminals 4 and 5 and ground.

• If greater than 3 ohm, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

3. Ignition ON, test for 4.8-5.2 V between each of the B107 Accelerator Pedal Position Sensor 5 V reference circuit terminals 1 and 2 and ground.

• If less than 4.8 V, test affected 5 V reference circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the K20 Engine Control Module.
• If greater than 5.2 V test affected 5 V reference circuit for short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.

4. Ignition ON, verify the scan tool APP sensor 1 and 2 voltages are less than 0.1 V.

• If greater than 0.1 V, test the B107 Accelerator Pedal Position Sensor 1 and 2 signal circuits terminal 3 and 6 for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.

5. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the 5 V reference circuit terminal 2 of the B107 Accelerator Pedal Position Sensor 1, verify the APP sensor 1 voltage is greater than 4.8 V.

• If less than 4.8 V, test the B107 Accelerator Pedal Position Sensor 1 signal circuit for an open or short to ground. If the circuit tests normal, replace the K20 Engine Control Module.

6. Install a 3 A fused jumper wire between the signal circuit terminal 6 and the 5 V reference circuit terminal 1 of the B107 Accelerator Pedal Position Sensor 2. Verify that the APP sensor 2 voltage is greater than 4.8 V.

• If less than 4.8 V, test the B107 Accelerator Pedal Position Sensor 2 signal circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the K20 Engine Control Module.

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)

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