Pinpoint Test B: DTC P0645 - Air Conditioning Clutch Relay (A/CCR) Control Circuit

Climate Control System

Pinpoint Tests

Pinpoint Test B: DTC P0645 - Air Conditioning Clutch Relay (A/CCR) Control Circuit

Refer to Wiring Diagram Set 54, Manual 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 from Bussed Electrical Center (BEC) fuse 47 (15A). When A/C is requested, and A/C line pressures allow, a ground is provided to the A/C clutch relay from the PCM through circuit 321 (GY/WH), 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 - AIR CONDITIONING CLUTCH RELAY (A/CCR) CONTROL CIRCUIT

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B1 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY


NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use the test probe.

- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between ground and the A/C clutch relay socket.




- Is the voltage greater than 10 volts?

Yes
CARRY OUT the A/C clutch relay component test.
If the relay tests OK, GO to B2.

No
VERIFY BEC fuse 47 (15A) is OK. If OK, INSTALL a new BEC. 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.

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B2 CHECK CIRCUIT 321 (GY/WH) FOR A SHORT TO VOLTAGE


- Ignition OFF.
- Disconnect: PCM C175b.
- Ignition ON.
- Measure the voltage between ground and PCM C175b-14, circuit 321 (GY/WH), harness side.




- Is any voltage present?

Yes
REPAIR circuit 321 (GY/WH) 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 321 (GY/WH) FOR A SHORT TO GROUND


- Ignition OFF.
- Measure the resistance between ground and PCM C175b-14, circuit 321 (GY/WH), harness side.




- Is the resistance greater than 10,000 ohms?

Yes
GO to B4.

No
REPAIR circuit 321 (GY/WH) 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 321 (GY/WH) FOR AN OPEN


NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use the test probe.

- Measure the resistance between A/C clutch relay socket, circuit 321 (GY/WH) and PCM C175b-14, circuit 321 (GY/WH), harness side.




- Is the resistance less tan 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 MODULE CONNECTION


- Clear the DTCs.
- Disconnect all the PCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- incorrectly seated connector.
- Connect and correctly seat all the PCM connectors.
- Operate the system.
- Does the concern return?

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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