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  • P2122 Low Voltage At The APP Sensor

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    Mopar1973Man

    By Mopar1973Man

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    P2122 LOW VOLTAGE AT THE APP SENSOR

    When Monitored and Set Condition:

    When Monitored: While the key is on and during engine operation.
    Set Condition: The APPS circuit voltage at the ECM goes below 0.13 volt for more than 2 seconds.

    POSSIBLE CAUSES

    • APPS
    • (K851) 5-VOLT SUPPLY CIRCUIT OPEN
    • (K22) SIGNAL CIRCUIT OPEN FROM ECM TO APPS
    • (K22) SIGNAL CIRCUIT SHORTED TO (K922) RETURN CIRCUIT
    • (K22) SIGNAL CIRCUIT SHORTED TO GROUND
    • (K22) SIGNAL CIRCUIT SHORTED TO (K914) SENSOR RETURN
    • (K851) 5-VOLT SUPPLY CIRCUIT SHORTED TO (K922) RETURN CIRCUIT
    • (K851) 5-VOLT SUPPLY CIRCUIT SHORTED TO (K914) SENSOR RETURN
    • (K851) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
    • (K22) SIGNAL CIRCUIT SHORTED TO (K565) IDLE CIRCUIT
    • (K22) SIGNAL CIRCUIT SHORTED TO (K556) NOT IDLE CIRCUIT
    • ECM
    • INTERMITTENT CONDITION
    • (K23) APPS NO. 1 SIGNAL CIRCUIT OPEN
    • (K852) APPS NO. 1 5-VOLT SUPPLY OPEN
    • (K23) APPS NO. 1 SIGNAL CIRCUIT SHORTED TO GROUND
    • (K23) APPS NO. 1 SIGNAL CIRCUIT SHORTED TO OTHER CIRCUITS
    • (K852) APPS NO. 1 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
    • (K852) APPS NO. 1 5-VOLT SUPPLY CIRCUIT SHORTED TO OTHER CIRCUITS
    • INTERMITTENT CONDITION

    DIAGNOSTIC PROCEDURE

    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 17
    2. Turn the ignition off. Disconnect the APPS harness connector.
      NOTE: Check connectors - Clean/repair as necessary.
      Measure the resistance between the (K22) signal circuit of the sensor to the (K851) 5-volt supply circuit of the sensor. Is the resistance between 1500 - 3000 Ohms with the accelerator pedal released?
      Yes --> Go To 3
      No --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    3. Measure the resistance between the (K22) signal circuit of the sensor to the (K851) 5-volt supply circuit of the sensor.
      NOTE: Released resistance must be at least 1000 Ohms greater than depressed resistance.
      Is the resistance between 200 - 1500 Ohms with the accelerator pedal depressed?
      Yes --> Go To 4
      No --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    4. Measure the resistance between the (K851) 5-volt supply circuit of the sensor and the (K922) return circuit of the sensor. Is the resistance between 2000 and 3000 Ohms, depressed as well as released?
      Yes --> Go To 5
      No --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    5. Connect a jumper wire between the (K22) signal circuit in the sensor harness connector and the (K851) 5-volt supply circuit in the sensor harness connector. With the DRBIII®, read DTCs. Did P2123 set?
      Yes --> Replace the APPS. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 6
    6. Disconnect the ECM harness connectors.
      NOTE: Check connectors - Clean/repair as necessary. Measure the resistance of the (K851) 5-volt supply 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 (K851) 5-volt supply circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    7. Measure the resistance of the (K22) signal circuit between the APPS harness connector and the ECM harness connector. Is the resistance less than 10 ohms?
      Yes --> Go To 8
      No --> Repair the open (K22) signal circuit from ECM to APPS harness connector. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    8. Measure the resistance between the (K22) signal circuit in the sensor harness connector and the (K922) return circuit in the sensor harness connector. Is the resistance less than 10 ohms?
      Yes --> Repair the (K22) signal circuit shorted to the (K922) return circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 9
    9. Measure the resistance between the (K22) signal circuit in the sensor harness connector and battery negative. Is the resistance less than 10 ohms?
      Yes --> Repair the (K22) signal circuit shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 10
    10. Measure the resistance between the (K22) signal circuit in the sensor harness connector and the (K914) sensor return circuit of the ECM harness connector. Is the resistance less than 10 ohms?
      Yes --> Repair the (K22) signal circuit shorted to the (K914) sensor return circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 11
    11. Measure the resistance between the (K851) 5-volt supply circuit in the sensor harness connector and the (K922) return circuit in the sensor harness connector. Is the resistance less than 10 ohms?
      Yes --> Repair the (K851) 5-volt supply circuit shorted to the (K922) return circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 12
    12. Measure the resistance between the (K851) 5-volt supply circuit in the sensor harness connector and battery negative. Is the resistance less than 10 ohms?
      |Yes --> Repair the (K851) 5-volt supply circuit shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 13
    13. Measure the resistance between the (K851) 5-volt supply circuit in the sensor harness connector and the (K914) sensor return circuit of the ECM harness connector. Is the resistance less than 10 ohms?
      Yes --> Repair the (K851) 5-volt supply circuit shorted to the (K914) sensor return circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 14
    14. Measure the resistance between the (K22) signal circuit in the sensor harness connector and the (K565) idle switch circuit in the sensor harness connector. Is the resistance less than 10 ohms?
      Yes --> Repair the (K22) signal circuit shorted to the (K565) idle circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 15
    15. Measure the resistance between the (K22) signal circuit in the sensor harness connector and the (K556) not idle switch circuit in the sensor harness connector. Is the resistance less than 10 ohms?
      Yes --> Repair the (K22) signal circuit shorted to the (K556) not idle circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 16
    16. Reconnect the ECM harness connectors. Ignition on, engine not running. Connect a jumper wire between the (K22) signal circuit in the sensor harness connector and the (K851) 5-volt supply circuit in the sensor harness connector. Did DTC P2123 set?
      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).
    17. 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 (K23) APPS No. 1 signal circuit between the APPS sensor harness connector and the ECM harness connector. Is the resistance less than 10 ohms?
      Yes --> Go To 18
      No --> Repair the (K23) APPS No. 1 signal circuit open. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    18. Measure the resistance of the (K852) APPS No. 1 5-volt supply circuit between the APPS sensor harness connector and the ECM harness connector. Is the resistance less than 10 ohms?
      Yes --> Go To 19
      No --> Repair the (K852) APPS No. 1 5-volt supply open. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    19. Measure the resistance between the (K23) APPS No. 1 signal circuit at the sensor harness connector and battery negative. Is the resistance greater than 100 k ohms?
      Yes --> Go To 20
      No --> Repair the (K23) APPS No. 1 signal circuit shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    20. Measure the resistance between the (K23) APPS No. 1 signal circuit at the sensor harness connector and all other circuits in the ECM harness connector. Is the resistance greater than 100 k ohms?
      Yes --> Go To 21
      No --> Repair the (K23) APPS No. 1 signal circuit shorted to other circuits. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    21. Measure the resistance between the (K852) APPS No. 1 5-volt supply circuit at the sensor harness connector and battery negative. Is the resistance greater than 100 k ohms?
      Yes --> Go To 22
      No --> Repair the (K852) APPS No. 1 5-volt supply circuit shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    22. Measure the resistance between the (K852) APPS No. 1 5-volt supply circuit at the sensor harness connector and all other circuits in the ECM harness connector. Is the resistance greater than 100 k ohms?
      Yes --> Go To 23
      No --> Repair the (K852) APPS No. 1 5-volt supply circuit shorted to other circuits. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    23. Reconnect the ECM harness connectors. Turn the ignition on. While monitoring with the DRBIII®, connect a jumper wire between the (K23) APPS No. 1 signal circuit at the sensor harness connector and the (K852) APPS No. 1 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 DTC P2123 set?
      Yes --> Go To 24
      No --> Replace and program the ECM in accordance with the Service Information. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    24. Reconnect the APPS harness connector. 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 and is the volta
      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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