Operation CHARM: Car repair manuals for everyone.
Home >> Chevy Truck >> 2006 >> HHR L4-2.4L >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P2123

P2123



DTC P2123

DTC DESCRIPTORS

DTC P2120
Accelerator Pedal Position (APP) Sensor 1 Circuit

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

IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection






TYPICAL SCAN TOOL DATA

APP Sensor 1 and 2:






CIRCUIT/SYSTEM DESCRIPTION
The throttle actuator control (TAC) system uses 2 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 the following circuits:
- A 5-Volt reference circuit
- A low reference circuit
- A signal circuit

Two processors are also used to monitor the TAC 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. Both processors monitor each other's data to verify that the indicated APP calculation is correct.

CONDITIONS FOR RUNNING THE DTC

P2120, P2122, P2123, P2125, P2127, P2128
- The system voltage is more than 5.23 volts.
- The ignition is in the Unlock/Accessory or Run position.
- DTC P0641 is not set.
- DTC P2120, P2122, P2123, P2125, P2127, P2128 run continuously when the above conditions are met.

P2138
- The system voltage is more than 5.23 volts.
- The ignition is in the Unlock/Accessory or Run position.
- DTC P0641, P0651, P2120, P2125 are not set.
- DTC P2138 runs continuously when the above conditions are met.

CONDITIONS FOR SETTING THE DTC

P2120
The APP sensor 1 voltage is less than 0.13 volt or more than 4.87 volts for more than 0.4 second.

P2122
The ECM detects that the APP sensor 1 voltage is less than 0.13 volt for more than 0.4 second.

P2123
The ECM detects that the APP sensor 1 voltage is more than 4.87 volts for more than 0.4 second.

P2125
The APP sensor 2 voltage is less than 0.13 volt or more than 4.87 volts for more than 0.4 second.

P2127
The ECM detects that the APP sensor 2 voltage is less than 0.13 volt for more than 0.4 second.

P2128
The ECM detects that the APP sensor 2 voltage is more than 4.87 volts for more than 0.4 second.

P2138
The voltage difference between APP sensor 1 and APP sensor 2 exceeds a predetermined value for more than 2 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
- The control module commands the TAC system to operate in the Reduced Engine Power mode.
- A message center or an indicator displays Reduced Engine Power.
- Under certain conditions the control module commands the engine OFF.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

CIRCUIT/SYSTEM VERIFICATION
- With the ignition ON, use a scan tool to observe the APP sensor 1 voltage with the accelerator pedal in the rest position. The voltage should be between 0.13-4.87 volts.
- With the ignition ON, observe the APP sensor 2 voltage with the accelerator pedal in the rest position with a scan tool. The voltage should be between 0.13-4.87 volts.

CIRCUIT/SYSTEM TESTING
1. Clear the DTCs with the scan tool. Operate the vehicle within the Conditions for Running the DTC or within the conditions that you observed from the Freeze Frame/Failure Records.
2. With the ignition ON, observe the APP sensor 1 voltage parameter with the accelerator pedal in the rest position. The voltage should be between 0.13-4.87 volts.
- If more than 4.87 volts, test the low reference for an open or a faulty ECM.
- If less than 0.13 volt, test the APP sensor 1 signal circuit for a short to ground or a faulty ECM.
3. With the ignition ON, observe the APP sensor 2 voltage parameter with the accelerator pedal in the rest position. The voltage should be between 0.13-4.87 volts.
- If more than 4.87 volts, test the low reference for an open or a faulty ECM.
- If less than 0.13 volt, test the APP sensor 2 signal circuit for a short to ground or a faulty ECM.
4. With the ignition ON, observe the DTCs.
- If DTC P2120 is the only code set, replace the ECM.
- If DTC P2125 is the only code set, replace the ECM.
5. Disconnect the accelerator pedal harness connector and verify APP sensor 1 and 2 voltages are less than 0.1 volt.
- If more than 0 volts, test the APP sensor 1 and 2 signal circuits for a short to voltage or a faulty ECM.
6. With the ignition ON, test for 4.8-5.2 volts between both 5-Volt reference circuits and the negative terminal of the battery.
- If more than 5.2 volts, test both 5-Volt reference circuits for a short to voltage or faulty ECM.
- If less than 4.8 volts, test both the 5-Volt reference circuits for an open or short to ground or a faulty ECM.
7. Install a 3-amp fused jumper wire between the signal circuit and the 5-Volt reference circuit of the APP sensor 1, and verify the APP sensor 1 voltage is greater than 4.8 volts.
- If less than 4.8 volts, test the APP sensor 1 signal circuit for an open, short to ground, or a faulty ECM.
8. Install a 3-amp fused jumper wire between the signal circuit and the 5-Volt reference circuit of the APP sensor 2, and verify that the APP sensor 2 voltage is greater than 4.8 volts.
- If less than 4.8 volts, test the APP sensor 2 signal circuit for an open, short to ground, or a faulty ECM.
9. If all circuits test normal, replace the accelerator pedal.

CIRCUIT/SYSTEM TESTING FOR P2138 ONLY
1. With the ignition OFF, disconnect the accelerator pedal harness connector and the ECM harness connector, and test for less than 5 ohms on each APP sensor circuit.
- If more than 5 ohms, repair the affected circuit or faulty ECM.
- If less than 5 ohms, test for a short between APP sensor 1 signal circuit and APP sensor 2 signal circuit.
2. If all circuits test normal, replace the accelerator pedal.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Accelerator Pedal with Position Sensor Replacement
- Control Module References. Verification Tests
pro multis · About Operation CHARM