Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC P2122: Accelerator Pedal Position (APP) Sensor 1 Circuit Low VoltageDTC 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
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
Accelerator Pedal Position (APP) Sensor 1 5-Volt Reference Circuit | P0122, P0222, P0641, P2110, P2135 | P2138 | P2122 | P0223, P0641, P2106, P2110, P2135 | -- |
Accelerator Pedal Position (APP) Sensor 2 5-Volt Reference Circuit | P0107, P0452, P0651, P2106 | P2138 | P2106, P2127 | P0651 | -- |
Accelerator Pedal Position (APP) Sensor 1 Signal | P2122 | P2138 | P2122 | P2123 | P2138 |
Accelerator Pedal Position (APP) Sensor 2 Signal | P2127 | P2138 | P2127 | P2106, P2138 | P2138 |
Accelerator Pedal Position (APP) Sensor 1 Low Reference | -- | -- | P2123 | -- | -- |
Accelerator Pedal Position (APP) Sensor 1 Low Reference | -- | -- | P2128 | -- | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: The engine is operating at idle. Parameter Normal Range: APP Sensor 1 0% Parameter Normal Range: APP Sensor 2 0% | |||
5-Volt Reference 1 | APP 1 0% | APP 1 0% | APP 1 14% |
5-Volt Reference 2 | APP 2 0% | APP 2 0% | APP 2 4% |
APP Sensor 1 Signal | APP 1 0% | APP 1 0% | APP 1 89% |
APP Sensor 2 Signal | APP 2 0% | APP 2 0% | APP 2 189% |
APP Sensor 1 Low Reference | -- | APP 1 88% | -- |
APP Sensor 2 Low Reference | -- | APP 2 186% | -- |
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 or P2123
| • | DTC P0641 is not set. |
| • | The ignition is ON or the engine is running. |
| • | The DTCs run continuously when the above conditions are met. |
P2127 or P2128
| • | DTC P0651 is not set. |
| • | The ignition is ON or the engine is running. |
| • | The DTCs run continuously when the above conditions are met. |
P2138
| • | The ignition is ON or the engine is running. |
| • | The DTC runs continuously when the above condition is met. |
Conditions for Setting the DTC
P2122
The ECM detects that the APP sensor 1 is less than 2.5 percent for less than 1 second.
P2123
The ECM detects that the APP sensor 1 is greater than 97.5 percent for less than 1 second.
P2127
The ECM detects that the APP sensor 2 is less than 2.5 percent for less than 1 second.
P2128
The ECM detects that the APP sensor 2 is greater than 60 percent for less than 1 second.
P2138
The ECM detects that APP sensor 1 and APP sensor 2 disagree greater 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. |
P2122 or P2123
The ECM uses APP sensor 2 for accelerator pedal position.
P2126 or P2127
The ECM uses APP sensor 1 for accelerator pedal position.
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
Connector End View Reference
Description and Operation
Throttle Actuator Control (TAC) System Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, observe the DTC information with a scan tool. Verify DTCs P0641 or P0651 are not set.
- Ignition ON, observe the scan tool APP Sensor parameters. Verify both of the APP sensor percentage parameters are at 0 percent.
- 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.
- 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.
- 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.
| ⇒ | If any DTC is set, refer to DTC P0641 or P0651 . |
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the accelerator pedal assembly.
- Ignition OFF, test for less than 5 ohms of resistance between the appropriate low reference circuit terminal listed below and ground.
- Ignition ON, test for 4.8-5.2 volts between the appropriate 5-volt reference circuit terminal listed below and ground.
- Verify the appropriate APP sensor percentage parameter is at 0%.
- Install a 3A fused jumper wire between the appropriate signal circuit terminal and the 5-volt reference circuit terminal listed below. Verify the APP sensor percentage parameter is greater than 85 percent.
- If all circuits test normal, test or replace the accelerator pedal assembly.
| • | APP1 sensor low reference circuit terminal 5 |
| • | APP2 sensor low reference circuit 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 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.
| • | APP1 sensor 5 volt reference circuit terminal 4 |
| • | APP2 sensor 5 volt reference circuit terminal 3 |
| ⇒ | 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 ECM. |
| ⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| • | APP1 sensor signal circuit terminal 6 |
| • | APP2 sensor signal circuit terminal 1 |
| • | APP1 sensor 5 volt reference circuit terminal 4 |
| • | APP2 sensor 5 volt reference circuit terminal 3 |
| ⇒ | If less than the specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for ECM replacement, setup, and programming
