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Diagnostic Routine M




Diagnostic Routine M

Diagnostic Overview

The Air Conditioning (AC) Is Inoperative

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 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

When an A/C (Air Conditioning) request is received by the PCM (Powertrain Control Module), the A/C (Air Conditioning) compressor clutch only engages through the A/C (Air Conditioning) clutch relay if all of these conditions are met:

- The PCM (Powertrain Control Module) does not detect excessively high or low refrigerant pressure from the A/C (Air Conditioning) pressure transducer.

- The PCM (Powertrain Control Module) does not detect excessively high engine coolant temperature.

- The PCM (Powertrain Control Module) does not detect an ambient air temperature below -1 C (30.2 F).

- The PCM (Powertrain Control Module) has not detected a WOT (Wide Open Throttle) condition.

- The HVAC (Heating, Ventilation, and Air Conditioning) module does not detect an evaporator discharge air temperature below 7.5 C (45.5 F).

Visual Inspection and Diagnostic Pre-checks

- Inspect the BJB (Battery Junction Box) fuse 62 (10A).

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

- Inspect for A/C (Air Conditioning) system discharged/low charge.

Pinpoint Test

1. CHECK THE A/C (Air Conditioning) SYSTEM PRESSURE

1. Ignition OFF.

2. With a manifold gauge set connected, check the A/C (Air Conditioning) system pressure.

Is the A/C (Air Conditioning) system pressure above 290 kPa (42 psi)?








2. CHECK THE A/C (Air Conditioning) PRESSURE SENSOR (ACP_PRESS) PID (Parameter Identification)

1. Ignition ON.

2. Using a scan tool, view PCM (Powertrain Control Module) PIDs (Parameter Identifications).

3. With a manifold gauge set connected, compare the pressure readings of the manifold gauge set and the PCM (Powertrain Control Module) PID (Parameter Identification) ACP_PRESS.

Are the pressure values of the manifold gauge set and the PID (Parameter Identification) similar?








3. CHECK THE A/C (Air Conditioning) EVAPORATOR TEMPERATURE (EVAP_TEMP) PID (Parameter Identification)

1. Allow the vehicle exterior and interior to stabilize to the ambient temperature.

2. Using a scan tool, view the HVAC (Heating, Ventilation, and Air Conditioning) module PIDs (Parameter Identifications).

3. Monitor the HVAC (Heating, Ventilation, and Air Conditioning) module PID (Parameter Identification) EVAP_TEMP.

Does the PID (Parameter Identification) read similar to the ambient temperature?








4. CHECK THE A/C (Air Conditioning) SWITCH (CC_SW_AC) PID (Parameter Identification) WITH THE A/C (Air Conditioning) ON

1. Using a scan tool, view the FCIM (Front Controls Interface Module) PIDs (Parameter Identifications).

2. Monitor the FCIM (Front Controls Interface Module) PID (Parameter Identification) CC_SW_AC.

3. Select panel, press the A/C (Air Conditioning) button (indicator on) on the HVAC (Heating, Ventilation, and Air Conditioning) controls.

Does the PID (Parameter Identification) read Active when the button is pressed?








5. CHECK THE A/C (Air Conditioning) REQUEST SIGNAL (AC_REQ) PID (Parameter Identification) WITH THE A/C (Air Conditioning) ON

1. Using a scan tool, view the PCM (Powertrain Control Module) PIDs (Parameter Identifications).

2. With the A/C (Air Conditioning) activated from the HVAC controls, monitor the PCM (Powertrain Control Module) PID (Parameter Identification) AC_REQ.

Does the PID (Parameter Identification) read ON?








6. CHECK THE A/C (Air Conditioning) COMPRESSOR COMMANDED STATE (ACC_CMD) PID (Parameter Identification) WITH THE A/C (Air Conditioning) ON

1. KOER (Key ON Engine Running).

2. Using a scan tool, view the PCM (Powertrain Control Module) PIDs (Parameter Identifications).

3. Turn the A/C (Air Conditioning) compressor on using the PCM (Powertrain Control Module) PID (Parameter Identification) ACC_CMD.

Does the A/C (Air Conditioning) compressor turn on?








7. CHECK THE VOLTAGE TO THE A/C (Air Conditioning) CLUTCH RELAY

1. Ignition OFF.

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

3. Measure:





Is the voltage greater than 11 volts?








8. BYPASS THE A/C (Air Conditioning) CLUTCH RELAY

1. Start the engine.

2. Connect a fused jumper wire:





Does the A/C (Air Conditioning) compressor clutch engage?








9. CHECK THE A/C (Air Conditioning) COMPRESSOR CLUTCH FIELD COIL VOLTAGE SUPPLY CIRCUIT FOR AN OPEN

1. Ignition OFF.

2. Disconnect: A/C (Air Conditioning) Compressor Clutch Field Coil.

3. Measure:





Is the voltage greater than 11 volts?








10. CHECK THE A/C (Air Conditioning) COMPRESSOR CLUTCH FIELD COIL GROUND CIRCUIT FOR AN OPEN

1. Measure:





Is the resistance less than 3 ohms?








11. 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 greater than 0.6 mm (0.0236 in)?








12. CHECK FOR CORRECT HVAC (Heating, Ventilation, and Air Conditioning) MODULE OPERATION

1. Ignition OFF.

2. Disconnect and inspect all HVAC (Heating, Ventilation, and Air Conditioning) 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 HVAC (Heating, Ventilation, and Air Conditioning) 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?








13. 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?







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