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Home >> Chrysler >> 2011 >> 300 C, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 85 (5.7L - DTCS P063A To P2127 - NGC - 3500 Cab & Chassis) >> Diagnosis and Testing >> P0643-Primary 5-Volt Supply Circuit High >> Diagnostic Test

Diagnostic Test

WARNING: This page is about a different car, the 2011 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
  1. ACTIVE DTC 
    NOTE:

    Improperly installed aftermarket accessories can cause this DTC to set. Check for any improperly installed aftermarket accessories before continuing with this test.

    1. Start the engine and allow it to idle for at least 60 seconds.
      WARNING:

      When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

    2. With a scan tool, select View DTCs.

      Is the DTC Active at this time?

      Yes 

      • Go To  2.

      No 

  2. (F855) PRIMARY 5-VOLT SUPPLY SHORTED TO VOLTAGE 
    Fig 1: Measuring Voltage On CKP Sensor 5-volt Supply Circuit
    GC0090900Courtesy of CHRYSLER LLC
    NOTE:

    Improperly installed aftermarket accessories can cause this DTC to set. Check for wiring added by customer.

    1. Turn the ignition off.
    2. Disconnect the C2 PCM harness connector.
    3. Disconnect all the Sensors that share the (F855) Primary 5-volt Supply circuit.
    4. Ignition on, engine not running.
    5. Measure the voltage on the (F855) Primary 5-volt Supply circuit at the CKP Sensor harness connector.

      Is there any voltage present?

      Yes 

      • Repair the short to voltage in the (F855) Primary 5-volt Supply circuit.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  3.
  3. POWERTRAIN CONTROL MODULE (PCM) 
    1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the related Sensors and the Powertrain Control Module (PCM).
    2. Look for any chafed, pierced, pinched, or partially broken wires.
    3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related Sensor and Control Module connectors.
    4. Refer to any Technical Service Bulletins that may apply.

      Were there any problems found?

      Yes 

      No 

      • Replace and program the Powertrain Control Module per Service Information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
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