Pinpoint Test B: DTC P0645

Climate Control System

Pinpoint Test B: DTC P0645

Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number

Normal Operation

Under normal operation, voltage is provided to the A/C clutch relay coil. When A/C is requested and A/C line pressures allow, a ground is provided to the A/C clutch relay coil from the PCM, energizing the A/C clutch relay.

- DTC P0645 (A/C Clutch Relay Control Circuit) - The DTC sets when the PCM grounds the relay circuit and excessive current draw is detected on the relay circuit. The DTC also sets when the relay circuit is OFF and no voltage is detected on the relay circuit. The PCM expects to detect voltage coming through the relay coil to the relay circuit when it is not grounding it.

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- A/C clutch relay
- PCM


PINPOINT TEST B: DTC P0645

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B1 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY


- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between ground and the A/C clutch relay socket pin 2, circuit 391 (RD/YE).




- Is the voltage greater than 10 volts?

Yes
CARRY OUT the A/C clutch relay component test.
Refer to Compressor Clutch Relay for component testing.
If the relay tests OK, GO to B2.

No
VERIFY Battery Junction Box (BJB) fuse 21 (15A) is OK. If OK, REPAIR circuit 391 (RD/YE) for an open. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation. Diagrams By Number

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B2 CHECK CIRCUIT 73 (OG/LB) FOR A SHORT TO VOLTAGE


- Ignition OFF.
- Disconnect: PCM C175B.
- Ignition ON.
- Measure the voltage between ground and PCM C175B-14, circuit 73 (OG/LB), harness side.




- Is any voltage present?

Yes
REPAIR circuit 73 (OG/LB) for a short to voltage. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

No
GO to B3.

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B3 CHECK CIRCUIT 73 (OG/LB) FOR A SHORT TO GROUND


- Ignition OFF.
- Measure the resistance between ground and PCM C175B-14, circuit 73 (OG/LB), harness side.




- Is the resistance greater than 10,000 ohms?

Yes
GO to B4.

No
REPAIR circuit 73 (OG/LB) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

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B4 CHECK CIRCUIT 73 (OG/LB) FOR AN OPEN


- Measure the resistance between A/C clutch relay socket, circuit 73 (OG/LB) and PCM C175B-14, circuit 73 (OG/LB), harness side.




- Is the resistance less than 5 ohms?

Yes
GO to B5.

No
REPAIR circuit 321 (GY/WH) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

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B5 CHECK THE PCM CONNECTION


- Disconnect all the PCM connectors.
- Inspect the module connectors for:

- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat all the PCM connectors.
- Clear the DTCs.
- Operate the system and verify the concern is still present.
- Is the concern still present?

Yes
INSTALL a new PCM. TEST the system for normal operation.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.

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