Pinpoint Test M: The Air Conditioning (A/C) is Inoperative
Climate Control System
Pinpoint Test M: The Air Conditioning (A/C) is Inoperative
Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, when the A/C button is pressed, a message is sent from the Front Controls Interface Module (FCIM) over the Medium Speed Controller Area Network (MS-CAN) bus to the HVAC module. The HVAC module then sends an A/C request message over the MS-CAN (Medium Speed Controller Area Network) bus to the Instrument Cluster (IC), then from the IC (Instrument Cluster) through the High Speed Controller Area Network (HS-CAN) bus to the PCM.
For vehicles equipped with navigation, when MAX A/C is selected on the touch screen, the Audio Control Module (ACM) sends a message over the MS-CAN (Medium Speed Controller Area Network) bus to the HVAC module that MAX A/C has been selected.
Voltage is provided to the A/C clutch relay switch. When the PCM energizes the relay, voltage is supplied to the A/C clutch from the relay. Ground is supplied for the A/C clutch.
The evaporator discharge air temperature sensor is used for A/C compressor cycling. An accurate evaporator discharge air temperature is critical for compressor engagement. The temperature measurement is used by the PCM to turn off the A/C compressor when the evaporator temperatures are cold enough to freeze the condensation.
When an A/C request is received by the PCM, the A/C compressor clutch will only be engaged through the A/C clutch relay if all of the following conditions are met:
- The PCM does not detect excessively high or low refrigerant pressure from the A/C pressure transducer.
- The PCM does not detect excessively high engine coolant temperature.
- The PCM does not detect an ambient air temperature below -1°C (30°F).
- The PCM has not detected a Wide Open Throttle (WOT) condition.
- The HVAC module does not detect an evaporator discharge air temperature below 2°C (36°F).
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- PCM
- HVAC module
- FCIM (Front Controls Interface Module)
- ACM (Audio Control Module)
- A/C evaporator discharge temperature sensor
- A/C pressure transducer
- A/C compressor clutch field coil
- A/C control relay
- A/C clutch air gap
PINPOINT TEST M : THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTE: Before carrying out the following test, diagnose any HVAC, PCM or IC (Instrument Cluster) DTCs.
NOTE: Before carrying out the following test, check that the A/C system pressure is above 290 kPa (42 psi). If the pressure is below 290 kPa (42 psi), refer to Fluorescent Dye Leak Detection Fluorescent Dye Leak Detection.
M1 CHECK THE A/C PRESSURE SENSOR (ACP_PRESS) PCM PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: ACP_PRESS PCM PID.
- With the manifold gauge set connected, compare the pressure readings of the manifold gauge set and the ACP_PRESS PID.
Are the pressure values of the manifold gauge set and the ACP_PRESS PID similar?
Yes
GO to M2.
No
INSTALL a new A/C pressure transducer. TEST the system for normal operation.
M2 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC PID
- Allow the vehicle exterior and interior to stabilize to the outside ambient temperature.
- Enter the following diagnostic mode on the scan tool: EVAP_TEMP HVAC PID.
Does the EVAP_TEMP HVAC PID read similar to the ambient temperature?
Yes
For 3.5L only, GO to M3.
For 3.5L Gasoline Turbocharged Direct Injection (GTDI) only, GO to M4.
No
INSTALL a new A/C evaporator discharge temperature sensor. TEST the system for normal operation.
M3 CHECK THE AIR CONDITIONING COMPRESSOR CYCLING SWITCH (ACCS) PCM PID WITH THE A/C ON
- Start the engine.
- Enter the following diagnostic mode on the scan tool: ACCS PCM PID.
- Select PANEL press the A/C button (indicator on) on the HVAC controls.
Does the ACCS PCM PID read ON?
Yes
GO to M7.
No
For vehicles equipped with navigation, GO to M5.
For vehicles not equipped with navigation, GO to M6.
M4 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQ) PCM PID WITH THE A/C ON
- Start the engine.
- Enter the following diagnostic mode on the scan tool: AC_REQ PCM PID.
- Select PANEL press the A/C button (indicator on) on the HVAC controls.
Does the AC_REQ PCM PID read ON?
Yes
GO to M8.
No
For vehicles equipped with navigation, GO to M5.
For vehicles not equipped with navigation, GO to M6.
M5 CHECK THE (A/C) SWITCH (CC_SW_AC) FCIM (Front Controls Interface Module) PID WITH THE A/C ON
NOTE: Before carrying out this test step, be sure all other FCIM (Front Controls Interface Module) button functions are operational. If all other buttons operate correctly, continue with this test step. If multiple buttons are inoperative and DTC U0256:00 is not present, install a new FCIM (Front Controls Interface Module). Test the system for normal operation. If DTC U0256:00 is present, diagnose the DTC first.
- Enter the following diagnostic mode on the scan tool: CC_SW_AC FCIM (Front Controls Interface Module) PID.
- Select PANEL press the A/C button (indicator on) on the HVAC controls.
Does the CC_SW_AC FCIM (Front Controls Interface Module) PID read Active?
Yes
GO to M15.
No
INSTALL a new FCIM (Front Controls Interface Module). TEST the system for normal operation.
M6 CHECK THE AUDIO AND HVAC CONTROLS
- Operate all the functions of the audio and HVAC controls.
Do all the functions operate correctly except both A/C and MAX A/C?
Yes
GO to M15.
No
If only the A/C or only the MAX A/C function is inoperative, INSTALL a new FCIM (Front Controls Interface Module). TEST the system for normal operation.
If A/C or MAX A/C and another HVAC function and any audio function is inoperative INSTALL a new FCIM (Front Controls Interface Module). TEST the system for normal operation.
If A/C and/or MAX A/C and any other HVAC function is inoperative and all audio controls operate correctly, GO to M14
M7 CHECK THE AIR CONDITIONING CLUTCH (WAC/ACCR) PCM PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: WAC/ACCR PCM PID.
- Select PANEL press the A/C button (indicator on) on the HVAC controls.
Does the WAC/ACCR PCM PID read ON?
Yes
GO to M9.
No
GO to M15.
M8 CHECK THE AIR CONDITIONING COMPRESSOR COMMANDED STATE (ACC_CMD) PCM PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: ACC_CMD PCM PID.
- Select PANEL press the A/C button (indicator on) on the HVAC controls.
Does the ACC_CMD PCM PID read ON?
Yes
GO to M9.
No
GO to M15.
M9 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Start the engine.
- Select PANEL and A/C on the HVAC module.
- Measure the voltage between A/C compressor clutch field coil C100-1, circuit CH401 (VT/WH), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to M10.
No
GO to M13.
M10 CHECK THE GROUND AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Measure the resistance between A/C compressor clutch field coil C100-2, circuit GD120 (BK/GN), harness side and ground.
Is the resistance less than 5 ohms?
Yes
GO to M11.
No
REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
M11 CHECK THE A/C COMPRESSOR CLUTCH FIELD COIL
- Measure the resistance between the A/C compressor clutch field coil C100 terminals, component side.
Is the resistance 2-5 ohms?
Yes
GO to M12.
No
INSTALL a new A/C compressor clutch field coil. TEST the system for normal operation.
M12 CHECK THE A/C COMPRESSOR CLUTCH FIELD COIL FOR A SHORT TO GROUND
- Measure the resistance between the A/C compressor clutch field coil C100 terminals, component side and ground.
Is the resistance greater than 10,000 ohms?
Yes
ADJUST the A/C compressor clutch gap. REFER to Air Conditioning (A/C) Clutch Air Gap Adjustment . TEST the system for normal operation.
No
INSTALL a new A/C compressor clutch field coil. TEST the system for normal operation.
M13 CHECK THE A/C CLUTCH RELAY FOR VOLTAGE
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between A/C clutch relay socket, circuit SBB24 (VT/RD) and ground.
Is the voltage greater than 10 volts?
Yes
CARRY OUT the A/C clutch relay component test.
If the relay tests OK, REPAIR circuit CH401 (VT/WH) for an open. TEST the system for normal operation.
No
VERIFY Battery Junction Box (BJB) fuse 24 (10A) is OK. If OK, REPAIR circuit SBB24 (VT/RD) for an open. TEST the system for normal operation. If not OK, Refer to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number
M14 CHECK THE MODULE CONNECTION
- Inspect the module connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat all the HVAC module connectors.
- Clear the DTCs.
- Operate the system and verify the concern is still present.
Is the concern still present?
Yes
INSTALL a new HVAC module. TEST the system for normal operation. If the condition returns, GO to M13.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
M15 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.