P2123

DTC P2120-P2123, P2125, P2127, P2128, or P1238

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 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 more 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.


Conditions for Clearing the DTC

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


Diagnostic Aids

If a shared 5-volt reference circuit is shorted to ground the engine will not start and the PCM will not communicate with the scan tool.


Reference Information
Schematic Reference

Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference

* Powertrain Control Module Connector End Views (Powertrain Control Module Connector End Views)
* Engine Controls Connector End Views (Engine Controls Connector End Views)

Description and Operation

Throttle Actuator Control (TAC) System Description (Throttle Actuator Control (TAC) System Description)
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 ON, observe that the APP sensor 1 scan tool parameter is between 0.75-0.80 volts.
2. Ignition ON, observe that the APP sensor 2 scan tool parameter is between 1.60-1.65 volts.
3. Observe both APP sensor parameters while pressing the accelerator pedal from the rest position to the floor. Both APP sensor parameters 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 5 ohms or less of resistance between ground and the low reference circuit terminals as listed below:

* APP sensor 1 terminal 3
* APP sensor 2 terminal 1


• 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 volts between ground and the 5-volt reference circuit terminals as listed below:

* APP sensor 1 terminal 6
* APP sensor 2 terminal 4


• 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 volts.

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


Important: The following test must be performed on both APP sensor signal circuits.


5. Install a 3A fused jumper wire between the 5-volt reference circuit and the APP sensor signal circuit terminal as listed below. Verify the correct scan tool APP sensor parameter as indicated.

* APP sensor 1 signal circuit terminal 5-5.0 volts
* APP sensor 2 signal circuit terminal 2-5.0 volts


• If less than the specified range, test the signal circuit for 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 PCM replacement, setup, and programming