LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Jeep >> 2021 >> Cherokee Trailhawk >> Repair and Diagnosis >> Engine Performance >> System >> 3.2L - DTCS P054C To P1129 >> DTC Troubleshooting >> P0645-A/C Control Circuit/Open >> Diagnostic Test
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Test

  1. CHECK FOR AN ACTIVE DTC 
    1. Start the engine and allow it to idle.
    2. Turn on the A/C or defrost to allow the A/C Compressor operation.
    3. With the scan tool, read DTCs and record on the repair order.

      Is the DTC active or pending?

      Yes 

      • Go To  2

      No 

  2. CHECK FOR BATTERY SUPPLY TO THE A/C CLUTCH RELAY CONTROL COIL 
    1. Using a DVOM, back probe and measure the voltage on the A/C Clutch Relay (C13) Control circuit at the PDC connector.
      NOTE:

      The relay must be commanded off when checking for voltage on the circuit. With the relay Low Side Driver control circuit commanded off the voltage should be approximately equal to Battery voltage on the A/C Clutch Relay (C13) Control circuit.

      Is the voltage approximately equal to Battery voltage?

      Yes 

      • Go To  3

      No 

      • Check all of the fuses in the PDC. If a fuse is open, replace the fuse and retest. If no problems are found with the fuses, check the Battery supply to the PDC. If no problems are found replace the Power Distribution Center (PDC) in accordance with the Service Information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  3. CHECK THE (C13) A/C CLUTCH CONTROL CIRCUIT FOR A SHORT TO ANOTHER VOLTAGE SOURCE 
    1. Turn the ignition off.
    2. Disconnect the PCM C1 harness connector.
    3. Disconnect the PDC C3 harness connector.
      CAUTION:

      Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.

    4. Connect the (special tool #10436, Adapter, GPEC Diagnostic).
    5. Check for continuity between the (C13) A/C Compressor Control circuit and all other 5.0 volt or 12.0 volt circuits at the GPEC Adaptor.

      Is there continuity between the (C13) A/C Compressor Control circuit and any other 5.0 volt or 12.0 volt circuit?

      Yes 

      • Repair the (C13) A/C Compressor Control circuit for a short to the circuit that showed continuity.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  4
  4. CHECK THE A/C CLUTCH RELAY (C13) CONTROL CIRCUIT FOR A SHORT TO GROUND 
    1. Check for continuity between ground and the (C13) A/C Clutch Relay Control circuit at the A/C Clutch Relay at the GPEC Adaptor?

      Is there continuity between ground and the (C13) A/C Clutch Relay Control circuit?

      Yes 

      • Repair the (C13) A/C Clutch Relay Control circuit for a short to ground.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  5
  5. CHECK THE (C13) A/C CLUTCH CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE 
    1. Measure the resistance of the (C13) A/C Clutch Control circuit between the PDC C3 harness connector and the GPEC Adaptor.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  6

      No 

      • Repair the (C13) A/C Clutch Control circuit for an open or high resistance.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  6. CHECK RELATED PCM AND COMPONENT CONNECTIONS 
    1. Disconnect all PCM harness connectors.
    2. Disconnect all related in-line harness connections (if equipped).
    3. Disconnect the related component harness connectors.
    4. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
      • Proper connector installation.
      • Damaged connector locks.
      • Corrosion.
      • Other signs of water intrusion.
      • Weather seal damage (if equipped).
      • Bent terminals.
      • Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
      • Terminals that have been pushed back into the connector cavity.
      • Check for spread terminals and verify proper terminal tension.

      Repair any conditions that are found.

    5. Connect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
    6. Connect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
    7. Connect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
    8. With the scan tool, erase DTCs.
    9. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
    10. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      No 

      • The wiring or poor connection problem has been repaired.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
scientia non olet · About LEMON Manuals