Diagnostic Routine B

Diagnostic Routine B

Diagnostic Overview

P0645:00

Refer to Wiring Diagram Set 54 for schematic and connector information Electrical Diagrams.

Normal Operation and Fault Conditions

Voltage is provided to the A/C (Air Conditioning) clutch relay coil. When A/C (Air Conditioning) is requested and A/C (Air Conditioning) line pressures allow, a ground is provided to the A/C (Air Conditioning) clutch relay coil from the PCM (Powertrain Control Module), energizing the A/C (Air Conditioning) clutch relay.

DTC Fault Trigger Conditions






Visual Inspection and Diagnostic Pre-checks

- Inspect BJB (Battery Junction Box) fuse 23 (5A).

Pinpoint Test

1. CHECK THE VOLTAGE TO THE A/C (Air Conditioning) CLUTCH RELAY COIL VOLTAGE SUPPLY CIRCUIT FOR AN OPEN

1. Ignition OFF.

2. Disconnect: A/C (Air Conditioning) Clutch Relay.

3. Measure:





Is the voltage greater than 11 volts?






2. SUBSTITUTE A KNOWN GOOD RELAY FOR THE A/C (Air Conditioning) CLUTCH RELAY

1. Substitute a known good relay for the A/C (Air Conditioning) clutch relay.

2. Using a scan tool, perform PCM (Powertrain Control Module) self-test.

Is DTC (Diagnostic Trouble Code) P0645:00 still present?






3. CHECK THE A/C (Air Conditioning) CLUTCH RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE

1. Ignition OFF.

2. Disconnect: PCM (Powertrain Control Module) C175B.

3. Ignition ON.

4. Measure:





Is any voltage present?






4. CHECK THE A/C (Air Conditioning) CLUTCH RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND

1. Ignition OFF.

2. Measure:





Is the resistance greater than 10,000 ohms?






5. CHECK THE A/C (Air Conditioning) CLUTCH RELAY CONTROL CIRCUIT FOR AN OPEN

1. Measure:





Is the resistance less than 3 ohms?






6. CHECK FOR CORRECT PCM (Powertrain Control Module) OPERATION

1. Ignition OFF.

2. Disconnect and inspect all the PCM (Powertrain Control Module) connectors.

3. Repair:

- corrosion (install new connector or terminals- clean module pins)
- damaged or bent pins- install new terminals/pins
- pushed-out pins- install new pins as necessary

4. Reconnect the PCM (Powertrain Control Module) connectors. Make sure they seat and latch correctly.

5. Operate the system and determine if the concern is still present.

Is the concern still present?