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P0642 Low Voltage At The #2 Sensor Supply Circuit

(1 review)

By Mopar1973Man

· 9,133 views

P0642 LOW VOLTAGE AT THE #2 SENSOR SUPPLY CIRCUIT

When Monitored and Set Condition:

When Monitored: With the key on.
Set Condition: Voltage detected on the #2 sensor supply circuit is below a calibrated value.

  • POSSIBLE CAUSES
  • FAN CLUTCH ASSEMBLY
  • (F856) 5-VOLT SHORTED TO GROUND
  • (F856) 5-VOLT SUPPLY SHORTED TO ANOTHER CIRCUIT
  • FAN DTC
  • INTERMITTENT CONDITION
  • ECM

DIAGNOSTIC PROCEDURE

  1. Disconnect the Fan clutch harness connector.
    NOTE: Check connectors - Clean/repair as necessary.
    With the DRBIII®, read DTCs. Did P0483 set?
    Yes --> Replace the Fan clutch assembly. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    No --> Go To 2
  2. Turn the ignition off. Disconnect the ECM harness connector.
    NOTE: Check connectors - Clean/repair as necessary.
    Measure the resistance between the (F856) #2 5-volt supply (fan speed sensor power) circuit in the sensor harness connector and battery negative. Is the resistance greater than 100k Ohms?
    Yes --> Go To 3
    No --> Repair the #2 (F856) 5-volt supply shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
  3. Measure the resistance between the sensor (F856) #2 5-volt supply (fan speed sensor power) circuit in the ECM harness connector to all other circuits in the ECM harness connectors Is the resistance greater than 100k Ohms?
    Yes --> Go To 4
    No --> Repair the 5-volt supply shorted to another circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
  4. Reconnect the ECM harness connectors. Reconnect the disconnected Fan harness connector. Turn the ignition on. With the DRBIII®, read DTCs. Is DTC P0483 set?
    Yes --> Repair the Fan DTC. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    No --> Go To 5
  5. Turn the ignition off. Disconnect the Fan harness connector. Turn the ignition on. Measure the voltage between the sensor (F856) #2 5-volt supply (fan speed sensor power) circuit at the fan clutch harness connector and the fan speed sensor ground. 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 the ECM. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).

    • User Feedback
    Newbie

    officerjones85

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       1 of 1 member found this review helpful 1 / 1 member

    This is awesome. Thank you for Ohms as well.

    • Like 2

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