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  • P2127 Low Voltage At The Throttle Validation Switch

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    P2127 LOW VOLTAGE AT THE THROTTLE VALIDATION SWITCH

    When Monitored and Set Condition:

    When Monitored: Key on.
    NOTE: This DTC will remain active until the accelerator pedal is cycled. Be sure to cycle the accelerator pedal after completing any repairs to this circuit and prior to checking DTC status with the. DRBIII®
    Set Condition: Both Idle and Not Idle switches are in the same state simultaneously for a calibrated amount of time.

    POSSIBLE CAUSES

    • APPS IDLE SWITCH
    • APPS NOT IDLE SWITCH
    • IDLE SWITCH CIRCUIT OPEN
    • NOT IDLE SWITCH CIRCUIT OPEN
    • APPS RETURN CIRCUIT OPEN
    • IDLE SWITCH CIRCUIT SHORTED TO VOLTAGE
    • NOT IDLE SWITCH CIRCUIT SHORTED TO VOLTAGE
    • ECM
    • APPS 2 SIGNAL CIRCUIT OPEN
    • INTERMITTENT CONDITION
    • 5-VOLT SUPPLY CIRCUIT OPEN
    • APPS 2 SIGNAL CIRCUIT SHORTED TO GROUND
    • APPS 2 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
    • APPS 2 SIGNAL CIRCUIT SHORTED
    • APPS 2 5-VOLT SUPPLY CIRCUIT SHORTED
    • APPS
    • ECM
    • INTERMITTENT CONDITION

    DIAGNOSTIC PROCEDURE

    NOTE: Refer to VERIFICATION TESTS for appropriate verification test procedures.

    1. The diesel engine uses two types of throttle position sensors, depending on transmission configuration. Is the throttle position sensor is located on the engine?
      Yes --> Go To 2
      No --> Go To 10
    2. Turn the ignition off. Disconnect the APPS harness connector. Turn the ignition on.
      NOTE: Check connectors - Clean/repair as necessary. Measure the voltage between the idle switch circuit of the APPS harness connector and sensor #1 return circuit. Is the voltage between 4.5 and 5.5 volts?
      Yes --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 3
    3. Measure the voltage between the not idle switch circuit of the APPS harness connector and sensor #1 return circuit. Is the voltage between 4.5 and 5.5 volts?
      Yes --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 4
    4. Turn the ignition off. Disconnect the ECM harness connector(s).
      NOTE: Check connectors - Clean/repair as necessary.
      Measure the resistance of the idle switch circuit between the APPS harness connector and the ECM harness connector. Is the resistance less than 10 Ohms?
      Yes --> Go To 5
      No --> Repair the open idle switch circuit from the ECM harness connector to the APPS harness connector. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    5. Measure the resistance of the not idle switch circuit between the APPS harness connector and the ECM harness connector. Is the resistance less than 10 Ohms?
      Yes --> Go To 6
      No --> Repair the open not idle switch circuit from the ECM harness connector to the APPS harness connector. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    6. Measure the resistance of the APPS #1 return circuit between the APPS harness connector and the ECM harness connector. Is the resistance less than 10 Ohms?
      Yes --> Go To 7
      No --> Repair the open APPS return circuit from the ECM harness connector to the APPS harness connector. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    7. Measure the voltage between the idle switch circuit of the APPS connector and battery negative. Is the voltage less than 1 volt?
      Yes --> Go To 8
      No --> Repair the shorted to voltage idle switch circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    8. Measure the voltage between the not idle switch circuit of the APPS connector and battery negative. Is the voltage less than 1 volt?
      Yes --> Go To 9
      No --> Repair the shorted to voltage not idle switch circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    9. Reconnect the ECM harness connector. Measure the voltage between the idle switch circuit of the APPS connector and APPS return circuit. Is the voltage between 4.5 and 5.5 volts?
      Yes --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure). Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Replace and program the ECM in accordance with the Service Information. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    10. Turn the ignition off. Disconnect the ECM harness connectors. Disconnect the APPS harness connector.
      NOTE: Check connectors - Clean/repair as necessary.
      Measure the resistance of the APPS 2 signal circuit between the APPS harness connector and the ECM harness connector Is the resistance less than 10 ohms?
      Yes --> Go To 11
      No --> Repair or replace the engine harness. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    11. Measure the resistance of the APPS 2 5-volt supply circuit between the APPS harness connector and the ECM harness connector. Is the resistance less than 10 ohms?
      Yes --> Go To 12
      No --> Repair the open 5-volt supply circuit or replace the wiring harness. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    12. Measure the resistance of the APPS 2 signal circuit between the APPS harness connector and battery negative. Is the resistance less than 100 ohms?
      Yes --> Go To 13
      No --> Repair or replace the engine harness. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    13. Measure the resistance of the APPS 2 5-volt supply circuit between the APPS harness connector and battery negative. Is the resistance less than 100 ohms?
      Yes --> Go To 14
      No --> Repair or replace the engine harness. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    14. Measure the resistance of the APPS 2 signal circuit between the APPS harness connector and all other circuits in the ECM harness connector. Is the resistance less than 100 ohms?
      Yes --> Go To 15
      No --> Repair or replace the engine harness. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    15. Measure the resistance of the APPS 2 5-volt supply circuit between the APPS harness connector and all other circuits in the ECM harness connector. Is the resistance less than 100 ohms?
      Yes --> Go To 16
      No --> Repair or replace the engine harness. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    16. Reconnect the ECM harness connectors. Ignition on, engine not running. While monitoring with the DRBIII®, connect a jumper wire between the APPS 2 signal circuit at the sensor harness connector and the APPS 2 5-volt supply circuit at the sensor harness connector.
      NOTE: With the sensor disconnected it is normal to have a APPS 1 and APPS 2 low voltage DTC set. Did a APPS 2 voltage too high DTC set?
      Yes --> Go To 17
      No --> Replace and program the ECM in accordance with the Service Information. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    17. Turn the ignition off. Reconnect the APPS harness connector. Ignition on, engine not running. Monitor the APPS 1 and APPS 2 voltage with the DRBIII® while depressing the throttle pedal. Is the voltage transition shown on the DRBIII® smooth while depressing the throttle
      Yes --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure). Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).

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