P2128

P2128-ACCELERATOR PEDAL POSITION SENSOR 2 CIRCUIT HIGH





For a complete wiring diagram refer to the Wiring Information Electrical Diagrams.

Theory of Operation

The throttle pedal produces two voltage signals proportional to the pedal movement. The primary signal varies between 0 and 5 volts and the secondary signal varies between 0 and 2.5 volts. The Engine Control Module uses the two signals to validate throttle pedal position to control engine fueling. The ECM illuminates the MIL lamp and ETC light solid immediately after the diagnostic runs and fails. Acceleration rate and Engine output are limited. The ECM will turn off the MIL lamp after the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:
With the ignition on and no other APPS No.2 DTCs present.

- Set Condition:
When APP Sensor No.2 voltage is above 4.8 volts for five seconds.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. APPS NO.2 VOLTAGE ABOVE 3.0 VOLTS

NOTE: When this DTC is Active the engine speed, torque, and vehicle speed are limited to a Limp in mode.

1. Ignition on, engine not running.
2. With a scan tool, read the APP Sensor No.2 voltage.

NOTE: Diagnose any 5-Volt Supply DTCs before continuing.

Is the voltage above 3.0 volts?

Yes

- Go To 2

No

- Go To 8

2. ACCELERATOR PEDAL POSITION SENSOR
1. Turn the ignition off.
2. Disconnect the APPS harness connector.
3. Ignition on, engine not running.
4. With a scan tool, monitor the Accelerator Pedal Position Sensor voltage.

Is the voltage above 0 volts?

Yes

- Go To 3

No

- Replace the APP Sensor Assembly. After installation is complete, use a scan tool and select the ETC RELEARN function to relearn the APPS values.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

3. (K29) APP SENSOR 2 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE




1. Turn the ignition off.
2. Disconnect the C2 ECM harness connector.
3. Ignition on, engine not running.
4. Measure the voltage on the (K29) APP Sensor 2 Signal circuit in the APP Sensor harness connector.

Is the voltage above 0 volts?

Yes

- Repair the short to battery voltage in the (K29) APP Sensor 2 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

No

- Go To 4

4. (K29) APPS 2 SIGNAL CIRCUIT SHORTED TO THE (F854) 5-VOLT SUPPLY CIRCUIT




1. Turn the ignition off.
2. Measure the resistance between the (K29) APP Sensor 2 Signal circuit and the (F854) 5-volt Supply circuit in the APP Sensor harness connector.

Is the resistance below 10k ohms?

Yes

- Repair the short between the (K29) APP Sensor 2 Signal circuit and the (F854) 5-volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

No

- Go To 5

5. (K29) APPS 2 SIGNAL CIRCUIT SHORTED TO THE (K852) 5-VOLT SUPPLY CIRCUIT




1. Measure the resistance between the (K29) APP Sensor 2 Signal circuit and the (K852) 5-volt Supply circuit in the APP Sensor harness connector.

Is the resistance below 10k ohms?

Yes

- Repair the short between the (K29) APP Sensor 2 Signal circuit and the (K852) 5-volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

No

- Go To 6

6. (K400) APP SENSOR 2 RETURN CIRCUIT OPEN




1. Measure the resistance of the (K400) APP Sensor 2 Return circuit from the APP Sensor harness connector to the C2 ECM harness connector.

Is the resistance below 5.0 ohms?

Yes

- Go To 7

No

- Repair the open or high resistance in the (K400) APP Sensor 2 Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

7. ECM

NOTE: Before continuing, check the ECM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

1. Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

No

- Replace and program the Engine Control Module.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

8. APP SENSOR NO.2 SWEEP
1. Ignition on, engine not running.
2. With a scan tool, monitor the Accelerator Pedal Position Sensor voltage.
3. Slowly press the Accelerator Pedal down.

Does voltage start at approximately 0.22 of a volt and go above 2.31 volts with a smooth transition?

Yes

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition Test

No

- Replace the APP Sensor Assembly. After installation is complete, use a scan tool and select the ETC RELEARN function to relearn the APPS values.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test