P2123
DTC P2122, P2123, P2127, P2128, or P2138
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) 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 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 a separate 5-volt reference and low reference circuit for each of the APP sensors.
The APP sensor 1 signal voltage increases as the pedal is depressed, from approximately 1 volt at rest to approximately 4 volts when fully depressed. The APP sensor 2 signal voltage increases as the pedal is depressed, from approximately 0.5 volt at rest to approximately 2 volts with the accelerator pedal fully depressed.
Conditions for Running the DTCs
* The ignition is ON or the engine is operating.
* The ignition voltage is greater than 7 volts.
* The DTCs run continuously once the above conditions are met.
Conditions for Setting the DTC
P2122
The APP sensor 1 voltage is less than 0.74 volts for greater than 2 seconds.
P2123
The APP sensor 1 voltage is greater than 4.82 volts for greater than 2 seconds.
P2127
The APP sensor 2 voltage is less than 0.63 volts for greater than 2 seconds.
P2128
The APP sensor 2 voltage is greater than 4.82 volts for greater than 2 seconds.
P2138
* The ECM detects that the voltage difference between APP sensor 1 and the calculated idle range is greater than 0.25 volts, with a released pedal.
* The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than 0.31 volts with a partially pressed pedal.
* The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than 1.70 volts with a fully pressed pedal.
* Any of the above conditions exist for greater than 2 seconds.
Action Taken When the DTC Sets
DTCs P2122, P2123, P2127, P2128, and P2138 are Type A DTCs.
Conditions for Clearing the DTC
DTCs P2122, P2123, P2127, P2128, and P2138 are Type A DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition OFF, open the hood to disable the Auto-Stop function.
2. Ignition ON, verify the scan tool hood position parameter displays Open.
• If the hood position does not display Open, refer to DTC P254F (P254F).
3. Ignition ON, observe the DTC information with a scan tool. DTC P0651, P0652, P0653, P0697, P0698, or P0699 should not be set.
• If a DTC is set, refer to DTC P0641-P0643, P0651-P0653, or P0697-P0699 (P0641).
4. Observe the scan tool APP Sensor voltage parameters. Verify both of the APP sensor voltages are between 0.4-4.5 V.
5. Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times. DTCs P2122, P2123, P2127, P2128, or P2138 should not set.
6. Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times. DTCs P2122, P2123, P2127, P2128, or P2138 should not set.
7. 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, open the hood to disable the Auto-Stop function.
2. Ignition ON, verify the scan tool hood position parameter displays Open.
• If the hood position does not display Open, refer to DTC P254F (P254F).
3. Ignition OFF, remove the fuse that supplies B+ to circuit terminal X2-56 of the ECM.
4. Disconnect the harness connector at the accelerator pedal assembly.
5. Test for less than 5 ohm between the low reference circuit terminals listed below and ground.
* Low reference circuit terminal A
* Low reference circuit terminal D
• If greater than the specified range, test the appropriate low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.
6. Install the fuse that supplies B+ to circuit terminal X2-56 of the ECM.
Note: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.
7. Ignition ON, test for 4.8-5.2 V between both 5-volt reference circuit terminals listed below and ground.
* 5 volt reference circuit terminal C
* 5 volt reference circuit terminal F
• If less than the specified range, test the appropriate 5-volt reference circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the ECM.
• If greater than the specified range, test the appropriate 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
8. Verify the appropriate APP sensor voltage parameter is at 0 V.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
9. Install a 3 A fused jumper wire between the appropriate signal circuit listed below and the 5-volt reference circuit terminal F. Verify the APP sensor voltage parameter is greater than 4.8 V.
* APP sensor 1 signal circuit terminal E
* APP sensor 2 signal circuit terminal B
• If less than the specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
10. If all circuits test normal, 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 (Programming and Relearning) for engine control module replacement, setup, and programming