P0645 A/C Control Circuit/Open

P0645 code - When the ignition switch is on, the Totally Integrated Power Module (TIPM) send a 12 volt signal to the Powertrain Control Module (PCM) on the A/C clutch relay control circuit.



The PCM grounds this signal to indicate a request for A/C compressor clutch operation. When monitored with the ignition on, Battery voltage greater than 10.0 volts, A/C being requested. And set condition this DTC an open or shorted condition is detected in the A/C clutch relay control circuit, one trip fault. Three good trips to turn off the MIL.

Possible causes P0645 code

- A/C clutch relay control circuit open
- A/C clutch relay control circuit shorted to ground
- Totally Integrated Power Module (TIPM)
- Powertrain Control Module (PCM)

Diagnose P0645 code

Step 1. Check for an active DTC
If there are any ASD/Main relay or system voltage DTCs present, diagnose this DTCs before proceeding with this test procedure.
Turn the ignition on with the scan tool read DTCs. Copy DTC and freeze frame information and erase DTCs. Active or pending DTCs may not allow A/C clutch actuation, make sure all DTCs are cleared before proceeding with this test procedure. With the scan tool actuate the A/C compressor, monitor the scan tool for at least two minutes. With the scan tool read DTCs.

Is the DTC active?

Yes, go to step 2.
No, perform the PCM intermittent condition.

Step 2. Check the A/C clutch relay control circuit for a short to ground
Turn the ignition off, disconnect the TIPM harness connector. Disconnect the PCM harness connector, check for continuity between ground and the A/C clutch relay control circuit at the PCM harness connector.

Is there continuity between ground and the A/C clutch relay control circuit?

Yes, repair the A/C clutch relay control circuit for a short to ground.
No, go to step 3.

Step 3. Check the A/C clutch control circuit for an open/high resistance
Measure the resistance of the A/C clutch control circuit between the TIPM harness connector and PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 4.
No, repair the A/C clutch control circuit for an open or high resistance.

Step 4. Totally Integrated Power Module (TIPM) actuation
Reconnect the TIPM harness connector. Turn the ignition on, connect a jumper between ground and the A/C clutch relay control circuit. The A/C compressor clutch should engage when the A/C clutch relay control circuit is jumped to ground.

Did the A/C compressor clutch engage when the A/C clutch relay control circuit is jumped to ground?

Yes, go to step 6.
No, go to step 5.

Step 5. Totally Integrated Power Module (TIPM)
Using the wiring/schematic as a guide, inspect the wiring and connectors between the Totally Integrated Power Module (TIPM) and the Powertrain Control Module (PCM). Look for any chafed, pierced, pinched or partially broken wires, look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related connectors. Perform any service bulletic that may apply.

Were any problems found?

Yes, repair as necessary.
No, replace and program the Totally Integrated Power Module (TIPM).

Step 6. Check related PCM and component connections

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