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Home >> Chevrolet >> 2007 >> Optra (CANADA) L4-2.0L >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P2128

P2128




DTC P2122, P2123, P2127, P2128, or P2138

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Strategy Based Diagnosis Strategy Based Diagnosis
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions

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 2 accelerator pedal position (APP) sensors. The APP sensors are mounted to the accelerator pedal assembly and are not serviceable. The APP sensors provide a signal voltage that changes relative to pedal position. The engine control module (ECM) supplies each APP sensor with a 5-volt reference circuit, a low reference circuit, and a signal circuit.

Both the APP sensors 1 and 2 signal percentages increase as the pedal is depressed, from approximately 0 percent at rest to above 75 percent when fully depressed.

Conditions for Running the DTC

P2122, P2123
* DTC P0641 is not set.
* The ignition is ON or the engine is operating.
* The DTCs run continuously when the above conditions are met.

P2127, P2128
* DTC P0651 is not set.
* The ignition is ON or the engine is operating.
* The DTCs run continuously when the above conditions are met.

P2138
* The ignition is ON or the engine is operating.
* The DTC runs continuously when the above condition is met.

Conditions for Setting the DTC

P2122

The ECM detects that the APP sensor 1 voltage is less than 0.25 volt for less than 1 second.

P2123

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

P2127

The ECM detects that the APP sensor 2 voltage is less than 0.25 volt for less than 1 second.

P2128

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

P2138
* The ECM detects that APP sensor 1 and APP sensor 2 disagree more than 4.5 percent for less than 1 second.
OR
* The ECM detects that both APP sensor 1 and APP sensor 2 are 4.5 percent greater than the learned minimum position for less than 1 second.

Action Taken When the DTC Sets

* DTCs P2122, P2123, P2127, P2128, and P2138 are Type A DTCs.
* The ECM commands the TAC system to operate in a Reduced Engine Power mode.
* The ECM commands the reduced engine power indicator ON.

DTC P2122 or P2123

The ECM uses accelerator pedal position (APP) sensor 2 for accelerator pedal position.

DTC P2126 or P2127

The ECM uses accelerator pedal position (APP) sensor 1 for accelerator pedal position.

DTC P2138

The ECM uses the lowest position recorded from the APP sensors for accelerator pedal position.

Conditions for Clearing the DTC

DTCs P2122, P2123, P2127, P2128, and P2138 are Type A DTCs.

Diagnostic Aids

* If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.
* The scan tool 5-volt reference parameter should display between 4.8-5.2 volts.

Reference Information
Schematic Reference

Engine Controls Schematics (w/Throttle Actuator Controls) Electrical DiagramsEngine Controls Schematics (w/o Throttle Actuator Control) Electrical Diagrams
Connector End View Reference

* Engine Control Module Connector End Views (w/ Throttle Actuator Control) Engine Control Module Connector End Views (w/ Throttle Actuator Control)Engine Control Module Connector End Views (w/o Throttle Actuator Control) Engine Control Module Connector End Views (w/o Throttle Actuator Control)
* Engine Controls Connector End Views (w/ Throttle Actuator Control) Engine Controls Connector End Views (w/ Throttle Actuator Control)Engine Controls Connector End Views (w/o Throttle Actuator Control) Engine Controls Connector End Views (w/o Throttle Actuator Control)

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

* Scan Tool Data List (w/ Throttle Actuator Control) Scan Tool Data List (w/ Throttle Actuator Control)Scan Tool Data List (w/o Throttle Actuator Control) Scan Tool Data List (w/o Throttle Actuator Control)
* Scan Tool Data Definitions (w/ Throttle Actuator Control) Scan Tool Data Definitions (w/ Throttle Actuator Control)Scan Tool Data Definitions (w/o Throttle Actuator Control) Scan Tool Data Definitions (w/o Throttle Actuator Control)
* Scan Tool Output Controls (w/ Throttle Actuator Control) Scan Tool Output Controls (w/ Throttle Actuator Control)Scan Tool Output Controls (w/o Throttle Actuator Control) Scan Tool Output Controls (w/o Throttle Actuator Control)

Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify DTCs P0641 or P0651 are not set.

• If DTCs P0641 or P0651 are set, refer to DTC P0641 or P0651 P0641.

2. Ignition ON, verify both of the scan tool APP sensor percentage parameters are at 0%.
3. 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.
4. 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.
5. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the accelerator pedal assembly.
2. Test for less than 5 ohms of resistance between the appropriate low reference circuit of the APP sensor and ground.

• If greater than the specified value, test the low reference circuit of the APP sensor for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.

Important: 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.


3. Ignition ON, load test for 4.8-5.2 volts between the appropriate 5-volt reference circuit of the APP sensor and ground.

• If less than the specified range, test the 5-volt reference circuit of the APP sensor 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 5-volt reference circuit of the APP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.

4. Verify the appropriate scan tool APP sensor percentage parameter is at 0%.

• If greater than the specified value, test the signal circuit of the applicable APP sensor for a short to voltage. If the circuit tests normal, replace the ECM.

5. Install a 3-amp fused jumper wire between the appropriate signal circuit and the 5-volt reference circuit. Verify the scan tool APP sensor percentage parameter is greater than 85%.

• If less than the specified value, test the appropriate signal circuit of the APP sensor for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

6. 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 Control Module References for engine control module replacement, setup, and programming

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