Diagnostic Routine N

Diagnostic Routine N

Diagnostic Overview

The Air Conditioning (AC) Is Always On - AC Compressor Does Not Cycle

Refer to Wiring Diagram Set 55 for schematic and connector information Electrical Diagrams.

Normal Operation and Fault Conditions

When the A/C (Air Conditioning) is requested, the FCIM (Front Controls Interface Module) sends the button press message over the I-CAN (Infotainment Controller Area Network) to the IPC (Instrument Panel Cluster). The IPC (Instrument Panel Cluster) then sends the button press message to BCM (Body Control Module) over the HS-CAN (High Speed Controller Area Network). The BCM (Body Control Module) then sends the button press message to the HVAC (Heating, Ventilation, and Air Conditioning) module over the MS-CAN (Medium Speed Controller Area Network). Lastly the HVAC (Heating, Ventilation, and Air Conditioning) module sends an A/C (Air Conditioning) request message through the MS-CAN (Medium Speed Controller Area Network) to the BCM (Body Control Module) and the BCM (Body Control Module) sends the A/C (Air Conditioning) request through the HS-CAN (High Speed Controller Area Network) to the PCM (Powertrain Control Module).

REFER to Control System Logic

REFER to Controls and Compressor Cycling

Visual Inspection and Diagnostic Pre-checks

- Inspect the A/C (Air Conditioning) clutch relay

Pinpoint Test

1. CHECK THE PCM (Powertrain Control Module) FOR DTCs (Diagnostic Trouble Codes)

1. Ignition ON.

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

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








2. CHECK THE A/C (Air Conditioning) COMPRESSOR CLUTCH ENGAGEMENT WITH RELAY DISCONNECTED

1. Ignition OFF.

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

3. KOER (Key ON Engine Running).

4. With the engine running, observe the A/C (Air Conditioning) compressor clutch.

Is the A/C (Air Conditioning) compressor on?








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

1. Ignition OFF.

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

3. Ignition ON.

4. Measure:





Is any voltage present?








4. CHECK THE A/C (Air Conditioning) COMPRESSOR CLUTCH AIR GAP

1. Measure the A/C (Air Conditioning) compressor clutch air gap at 3 equally spaced locations between the clutch hub and the A/C (Air Conditioning) compressor clutch pulley.





Is the A/C (Air Conditioning) compressor clutch air gap less than 0.35 mm (0.0138 in)?








5. CHECK THE A/C (Air Conditioning) CLUTCH RELAY FUNCTIONALITY

1. Using a known good A/C (Air Conditioning) clutch relay, check the A/C (Air Conditioning) compressor clutch for correct operation.

Is the A/C (Air Conditioning) compressor on?








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

1. Ignition OFF.

2. Disconnect and inspect all 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?