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






TYPICAL SCAN TOOL DATA

APP Sensor 1:




APP Sensor 2:






CIRCUIT/SYSTEM DESCRIPTION
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal control assembly. Two APP sensors, APP sensors 1 and 2, are used to monitor the accelerator pedal position. Each sensor has the following circuits:
- A 5-Volt reference circuit
- A low reference circuit
- A signal circuit

The engine control monitor (ECM) uses the APP sensors input to determine the amount of acceleration or deceleration that is desired. Refer to Throttle Actuator Control (TAC) System Description for further information on the TAC system.

CONDITIONS FOR RUNNING DTC

DTCs P2120, P2122, P2123, P2125, P2127, P2128
- DTC P0601, P0602, P0603, P0604, P0606, P060D, P062F, P0641, or P0651 are not set.
- The ignition is ON.
- The battery voltage is more than 5.23 volts.
- DTC P2122, P2123, P2127, P2128 run continuously when the above conditions are met.

DTC P2138
- DTC P0601, P0602, P0603, P0604, P0606, P060D, P062F, P0641, P0651, P2120, P2122, P2123, P2125, P2127 or P2128 are not set.
- The ignition is ON.
- The battery voltage is more than 5.23 volts.
- DTC P2138 runs continuously when the above conditions are met.

CONDITIONS FOR SETTING DTC

DTC P2120
The ECM detects that the APP sensor 1 voltage is less than 0.33 volt or more than 4.5 volts for more than or equal to 12.5 milliseconds.

DTC P2122
The ECM detects that the APP sensor 1 voltage is less than 0.33 volt for more than or equal to 12.5 milliseconds.

DTC P2123
The ECM detects that the APP sensor 1 voltage is more than 4.5 volts for more than or equal to 12.5 milliseconds.

DTC P2125
The ECM detects that the APP sensor 1 voltage is less than 0.33 volt or more than 4.5 volts for more than or equal to 12.5 milliseconds.

DTC P2127
The ECM detects that the APP sensor 2 voltage is less than or equal to 0.33 volt for more than or equal to 12.5 milliseconds.

DTC P2128
The ECM detects that the APP sensor 2 voltage is more than 4.5 volts for more than or equal to 12.5 seconds.

DTC P2138
The voltage difference between APP sensor 1 and APP sensor 2 exceeds a value of 5 percent with the pedal in the released position, or 10 percent with the pedal at wide open throttle (WOT) for less than 1 second.

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
1. If DTCs P0641 or P0651 are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis. Diagnostic Trouble Code Descriptions
2. With the ignition ON, use a scan tool to observe the APP sensor 1 for a normal voltage range between 0.89-4.57 volts.
3. With the ignition ON, use a scan tool to observe the APP sensor 2 for a normal voltage range between 0.41-2.19 volts.
4. With the ignition ON, use a scan tool to observe APP sensors 1 and 2 agree.
5. With the ignition ON, use a scan tool to compare APP sensors 1 and 2 percentages. Verify that they do not differ more than 5 percent when a slow pedal sweep is performed.

CIRCUIT/SYSTEM TESTING for DTCs P2120, P2122, P2123, P2125, P2127, or P2128
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, perform several full pedal sweeps and observe the DTCs information.
- If DTC P2120 is the only code set, replace the control module.
- If DTC P2125 is the only code set, replace the control module.
3. With the ignition OFF, disconnect the harness connector at the APP sensor. Allow at least 60 seconds for the ECM to power down. Test for less than 3 ohms of resistance between the applicable low reference circuit and ground.
- If greater than 3 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the control module.
4. With ignition ON, test for 4.8-5.2 volts between the applicable APP sensor 5-Volt reference circuit and ground.
- If less than 4.8 volts, test the 5-Volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the control module.
- If greater than 5.2 volts, test the 5-Volt reference circuit for a short to voltage. If the circuit tests normal, replace the control module.
5. Verify that the scan tool APP Sensor 1 parameter is less than 0.02 volt.
- If greater than 0.02 volt, then test the signal circuit for a short to voltage. If the circuit tests normal, replace the control module.
6. Install a 3-amp fused jumper wire between the APP 1 signal circuit and the APP 1 5-Volt reference circuit. verify that the scan tool APP sensor parameter is more than 4.5 volts.
- If less than 4.5 volts, test the APP 1 signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the control module.
7. Verify that the scan tool APP Sensor 2 parameter is more than 4.5 volts.
- If less than 4.5 volts, test the signal circuit for a short to ground. If the circuit tests normal, replace the control module.
8. Install a 3-amp fused jumper wire between the APP sensor 2 signal circuit and the APP 2 low reference circuit. Verify that the scan tool APP Sensor 2 parameter is less than 4.5 volts.
- If more than 4.5 volts, test the APP sensor 2 signal circuit for an open/high resistance. If the circuit tests normal, replace the control module.
- If less than 4.5 volts, replace the accelerator pedal assembly.

CIRCUIT/SYSTEM TESTING FOR P2138 ONLY
1. With the ignition OFF, disconnect the accelerator pedal sensor and the ECM harness connectors, test for infinite resistance between APP sensor 1 signal circuit and APP sensor 2 signal circuit.
- If less than infinite resistance, repair the short between APP sensor 1 signal circuit and APP sensor 2 signal circuits.
2. With the ignition OFF, and the accelerator pedal and ECM harness connectors still disconnected, measure for a resistance value of less than 5 ohms on each APP sensor circuit.
- If more than 5 ohms, repair the circuit with the high resistance. If all circuits test normal, replace the accelerator pedal assembly.

COMPONENT TEST

Dynamic Test
1. Install a 3-amp fused jumper wire between the 5-Volt reference terminal of the applicable APP sensor and 5 volts. Install a jumper wire between the low reference terminal and a ground.
2. Sweep the sensor through the entire range while monitoring the voltage between the signal terminal and the low reference terminal with a DMM. The voltage should vary between 0.40-4.55 volts with out an spikes or dropouts.
- If the voltage is not within the specified range or is erratic, replace the APP sensor.

REPAIR INSTRUCTION

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Accelerator Pedal with Position Sensor Replacement
- Control Module References for ECM replacement, setup, and programming Verification Tests
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