P2121

DTC P2120-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 P2121
- Accelerator Pedal Position (APP) Sensor 1 Performance

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 2 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 powertrain control module (PCM) 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 0.75 volts at rest to about 4 volts when fully depressed. The APP sensor 2 signal voltage increases as the pedal is depressed, from approximately 1.6 volts at rest to greater than 4.8 volts with the accelerator pedal fully depressed.

Conditions for Running the DTC

* The ignition is ON or the engine is running.
* The DTCs runs continuously when the above condition is met.

Conditions for Setting the DTC

P2120
* The PCM detects that the APP sensor 1 voltage is less than 0.2 volts for less than 1 second.
OR
* The PCM detects that the APP sensor 1 voltage is greater than 4.8 volts for less than 1 second.

P2121
* The difference between the APP sensor 1 and the APP sensor 2 voltage is less than 0.4 volts for less than 1 second.
OR
* The difference between the APP sensor 1 and the APP sensor 2 voltage is greater than 1.2 volts for less than 1 second.

P2122

The PCM detects that the APP sensor 1 voltage is less than 0.2 volts for less than 1 second.

P2123

The PCM detects that the APP sensor 1 voltage is greater than 4.8 volts for less than 1 second.

P2125
* The PCM detects that the APP sensor 2 voltage is less than 0.5 volts for less than 1 second.
OR
* The PCM detects that the APP sensor 2 voltage is greater than 4.8 volts for less than 1 second.

P2127

The PCM detects that the APP sensor 2 voltage is less than 0.5 volts for less than 1 second.

P2128

The PCM detects that the APP sensor 2 voltage is greater than 4.8 volts for less than 1 second.

P2138
* The PCM detects that the difference between APP sensor 1 and APP sensor 2 is less than 0.2 volts for greater than 2 seconds.
* The PCM detects that the APP sensor 1 voltage is less than 0.2 volts for greater than 2 seconds.
* The PCM detects that the APP sensor 2 voltage is less than 0.5 volts for greater than 2 seconds.

Action Taken When the DTC Sets

* DTC P2120, P2121, P2122, P2123, P2125, P2127, P2128 and P2138 are Type A DTCs.
* The PCM enters the Fail-Safe function operating in the Reduced Engine Power Mode. The throttle valve return spring will close the throttle valve to the idle position with the TP sensor 1 angle defaulted to 19 percent.

Conditions for Clearing the DTC

DTC P2120, P2121, P2122, P2123, P2125, P2127, P2128 and P2138 are Type A DTCs.

Diagnostic Aids

DTCs P0606 and P0607 indicate the 5-volt reference circuit was shorted to ground. The engine may not start and the PCM may not communicate with the scan tool during a shot to ground in the 5-volt reference circuit.

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 scan tool APP sensor 1 parameter. The reading should be between 0.75-0.80 volt.
2. Ignition ON, observe the scan tool APP sensor 2 parameter. The reading should be between 1.60-1.65 V.
3. Observe both scan tool APP sensor parameters while pressing the accelerator pedal from the rest position to the floor. Both APP senor readings should change.
4. Rapidly depress the accelerator pedal from the rest position to the floor and release the pedal. Repeat the procedure several times. DTCs P2120, P2121, P2122, P2123, P2125, P2127, P2128 and P2138 should not set.
5. Slowly depress the accelerator pedal to the floor and then slowly return the pedal to the rest position. Repeat the procedure several times. P2120, P2121, P2122, P2123, P2125, P2127, P2128 and 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, test for less than 10 ohm between the low reference circuit terminal listed below and ground G104.

* APP sensor 1 terminal 5
* APP sensor 2 terminal 2

• If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the PCM.

3. Ignition ON, test for 4.8-5.2 V between the 5-volt reference circuit terminal listed below and ground.

* APP sensor 1 terminal 4
* APP sensor 2 terminal 1

• If less than the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the PCM.
• If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the PCM.

4. Verify both scan tool APP sensor parameters are 0 V.

• If greater than the specified range, test the APP sensor signal circuit for a short to voltage. If the circuit tests normal, replace the PCM.

5. Install a 3 A fused jumper wire between the 5-volt reference circuit terminal 4 and the appropriate APP sensor signal circuit terminal listed below. Verify the scan tool APP sensor parameter is 5 V.

* APP sensor 1 signal circuit terminal 6
* APP sensor 2 signal circuit terminal 3

• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PCM.

6. If all circuits 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 (Programming and Relearning) for control module replacement, setup, and programming