P2122
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) 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 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 and P2123
* DTC P0642, or P0643 is not set.
* The ignition is ON.
* The DTCs run continuously when the above conditions are met.
P2127 and P2128
* DTC P0652, or P0653 is not set.
* The ignition is ON.
* The DTCs run continuously when the above conditions are met.
P2138
* DTCs P0642, P0643, P0652, or P0653 is not set.
* The ignition is ON.
* The DTC runs continuously when the above conditions are met.
Conditions for Setting the DTC
P2122
The ECM detects that APP sensor 1 voltage is less than 0.61 V for greater than 0.5 s.
P2123
The ECM detects that APP sensor 1 voltage is greater than 4.59 V for greater than 0.5 s.
P2127
The ECM detects that APP sensor 2 voltage is less than 0.10 V for greater than 0.5 s.
P2128
The ECM detects that APP sensor 2 voltage is greater than 2.5 V for greater than 0.5 s.
P2138
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, P2123, P2127, P2128 and P2138 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, P2123, P2127, P2128, and P2138 are Type A DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
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
Circuit/System Verification
1. Ignition ON.
2. Verify that DTC P0697, or P06A3 is not set.
• If any of the DTCs are set
Refer to DTC P0641, P0651, P0697, or P06A3 (ECM) Powertrain Management (ECM).
• If none of the DTCs are set
3. Verify the scan tool APP Sensor 1 parameter. The reading should be between 0.32-4.87 V, and change with the accelerator pedal input.
4. Verify the scan tool APP Sensor 2 parameter. The reading should be between 0.16-2.30 V, and change with the accelerator pedal input.
• If the reading does not change
Refer to Circuit/System Testing.
• If the reading does change
5. 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.
6. Verify the DTC does not set.
• If the DTC sets
Refer to Circuit/System Testing.
• If the DTC does not set
7. All OK.
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B107 Accelerator Pedal Position Sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 5 ohms between each low reference circuit terminal listed below and ground.
* Low reference circuit terminal 4
* Low reference circuit terminal 5
• If 5 ohms or greater
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 ohms in the low reference circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.
• If less than 5 ohms
3. Ignition ON.
4. Test for 4.8-5.2 V between each 5 V reference circuit terminal listed below and ground.
* 5 V reference circuit terminal 1
* 5 V reference circuit terminal 2
• If less than 4.8 V
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the 5 V reference circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.
• If greater than 5.2 V
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the 5 V reference circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 Engine Control Module.
• If between 4.8-5.2 V
5. Verify the scan tool APP sensor 1 and 2 voltage parameter is less than 0.1 V.
• If 0.1 V or greater
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal listed below and ground.
* APP sensor 1 signal circuit terminal 3
* APP sensor 2 signal circuit terminal 6
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 Engine Control Module.
• If less than 0.1 V
6. Install a 3 A fused jumper wire between each signal circuit terminal listed below and the 5 V reference circuit terminal 1.
* APP sensor 1 signal circuit terminal 3
* APP sensor 2 signal circuit terminal 6
7. Verify the scan tool APP sensor 1 and 2 voltage parameter is greater than 4.8 V.
• If 4.8 V or less
1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the signal circuit terminal and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.
• If greater than 4.8 V
8. Test or replace the B107 Accelerator Pedal Position Sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Accelerator Pedal Position Sensor Replacement Service and Repair
* Control Module References Control Module References for ECM replacement, programming, and setup.