P2123

P2123-ACCELERATOR PEDAL POSITION SENSOR 1 CIRCUIT HIGH





For a complete wiring diagram Refer to Diagrams/Electrical.

Theory of Operation


The throttle pedal produces two voltage signals proportional to the pedal movement. The voltages are created by electronic circuitry within the pedal assembly. 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 immediately after the diagnostic runs and fails. During this time the customer will be in a limp home mode. 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.1 DTCs present.

- Set Condition:
When APP Sensor No.1 voltage is too high. Engine will additionally idle if the brake pedal is pressed or has failed. Acceleration rate and Engine output are limited. One trip fault and the code will set within 5 seconds. ETC light is flashing.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview .


Diagnostic Test


1. APPS NO.1 VOLTAGE ABOVE 4.8 VOLTS
NOTE: When this DTC is Active the engine speed, torque, and vehicle speed are limited to a Limp in mode.

Ignition on, engine not running.
With a scan tool, read the APP Sensor No.1 voltage.
Is the voltage above 4.8 volts?

Yes


- Go To 2


No


- Go To 8



2. ACCELERATOR PEDAL POSITION SENSOR
Turn the Ignition off.
Disconnect the APP Sensor harness connector.
Ignition on, engine not running.
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. (K23) APP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE




Turn the ignition off.
Disconnect the C2 ECM harness connectors.
Ignition on, engine not running.
Measure the voltage on the (K23) APP Sensor No.1 Signal circuit in the APP Sensor harness connector.
Is the voltage above 0 volts?

Yes


- Repair the short to battery voltage in the (K23) APP Sensor No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


No


- Go To 4



4. (K23) APPS NO.1 SIGNAL CIRCUIT SHORTED TO THE (K852) 5-VOLT SUPPLY CIRCUIT




Turn the ignition off.
Measure the resistance between the (K23) APP Sensor No.1 Signal circuit and the (K852) 5-volt Supply circuit in the APP Sensor harness connector.
Is the resistance below 100 ohms?

Yes


- Repair the short between the (K23) APP Sensor No.1 Signal circuit and the (K852) 5-volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


No


- Go To 5



5. (K23) APPS NO.1 SIGNAL CIRCUIT SHORTED TO THE (F854) 5-VOLT SUPPLY CIRCUIT




Measure the resistance between the (K23) APP Sensor No.1 Signal circuit and the (F854) 5-volt Supply circuit in the APP Sensor harness connector.
Is the resistance below 100 ohms?

Yes


- Repair the short between the (K23) APP Sensor No.1 Signal circuit and the (F854) 5-volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


No


- Go To 6



6. (K167) APP SENSOR NO.1 RETURN CIRCUIT OPEN
Measure the resistance of the (K167) APP Sensor No.1 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 in the (K167) APP Sensor No.1 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.

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.1 SWEEP
Ignition on, engine not running.
With a scan tool, monitor the Accelerator Pedal Position Sensor voltage.
Slowly press the Accelerator Pedal down.
Does voltage start at approximately 0.45 of a volt and go above 4.6 volts with a smooth transition?

Yes


- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition


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