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 [1][2]Diagrams By Number.
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information [1][2]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 all 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 coil and switch contacts. When A/C is requested and A/C line pressures allow, a ground is provided to the A/C clutch relay coil from the PCM, energizing the A/C clutch relay. 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 temperature sensor is used for A/C compressor cycling. An accurate evaporator temperature is critical for compressor engagement. The temperature measurement is used by the PCM to turn off the A/C compressor before 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 7.5°C (45.5°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)
- Evaporator discharge air temperature sensor
- A/C pressure transducer
- A/C compressor clutch field coil
- A/C control relay
- A/C compressor clutch air gap
PINPOINT TEST M : THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTE: Before carrying out the following test, diagnose any HVAC, PCM, ACM (Audio Control Module) , FCIM (Front Controls Interface Module) 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 PCM PID.
Are the pressure values of the manifold gauge set and the ACP_PRESS PCM 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
GO to M3.
No
INSTALL a new Evaporator discharge air temperature sensor. TEST the system for normal operation.
M3 CHECK THE (A/C) SWITCH (CC_SW_AC) FCIM (Front Controls Interface Module) PID WITH THE A/C ON
- 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 M4.
No
INSTALL a new FCIM (Front Controls Interface Module). TEST the system for normal operation.
M4 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQ) PCM PID WITH THE A/C ON
- 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
For vehicles equipped with navigation, GO to M5.
For vehicles not equipped with navigation, GO to M6.
No
GO to M16.
M5 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQ) PCM PID WITH MAX A/C OPERATION
- Enter the following diagnostic mode on the scan tool: AC_REQ PCM PID.
- Select MAX A/C on the navigation screen.
Does the AC_REQ PCM PID read ON?
Yes
GO to M6.
No
INSTALL a new ACM (Audio Control Module). TEST the system for normal operation.
M6 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 M7.
No
GO to M17.
M7 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 M8.
No
CARRY OUT the A/C clutch relay component test.
If the relay tests OK, GO to M11.
M8 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 GD123 (BK/GY), harness side and ground.
Is the resistance less than 5 ohms?
Yes
GO to M9.
No
REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
M9 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 M10.
No
INSTALL a new A/C compressor clutch field coil. TEST the system for normal operation.
M10 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.
M11 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY SWITCH CONTACTS
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between A/C clutch relay socket, circuit SBB25 (RD) and ground.
Is the voltage greater than 10 volts?
Yes
GO to M12.
No
VERIFY Battery Junction Box (BJB) fuse 25 (10A) is OK. If OK, REPAIR circuit SBB25 (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 [1][2]Diagrams By Number.
M12 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY COIL
- Measure the voltage between ground and the A/C clutch relay socket, circuit CBB46 (WH/BU).
Is the voltage greater than 10 volts?
Yes
GO to M13.
No
REPAIR circuit CBB46 (WH/BU) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
M13 CHECK CIRCUIT CH401 (VT/WH) FOR AN OPEN
- Measure the resistance between A/C clutch relay socket, circuit CH401 (VT/WH) and A/C compressor clutch field coil C100-1, circuit CH401 (VT/WH), harness side.
Is the resistance greater than 10,000 ohms?
Yes
GO to M14.
No
REPAIR circuit CH401 (VT/WH) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
M14 CHECK CIRCUIT CH302 (WH/BN) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: (5.0L, 5.4L) PCM C175B.
- Disconnect: (3.7L) PCM C1381B.
- Ignition ON.
- Measure the voltage between ground and:
- For 5.0L and 5.4L, PCM C175B-12, circuit CH302 (WH/BN), harness side.
- For 3.7L, PCM C1381B-12, circuit CH302 (WH/BN), harness side.
Is any voltage present?
Yes
REPAIR circuit CH302 (WH/BN) for a short to voltage. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
GO to M15.
M15 CHECK CIRCUIT CH302 (WH/BN) FOR AN OPEN
- Measure the resistance between A/C clutch relay socket, circuit CH302 (WH/BN) and:
- For 5.0L and 5.4L, PCM C175B-12, circuit CH302 (WH/BN), harness side.
- For 3.7L, PCM C1381B-12, circuit CH302 (WH/BN), harness side.
Is the resistance less than 5 ohms?
Yes
GO to M17.
No
REPAIR circuit CH302 (WH/BN) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
M16 CHECK THE HVAC MODULE CONNECTION
- Inspect the HVAC 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.
M17 CHECK THE PCM CONNECTION
- Disconnect all the PCM connectors.
- Inspect the HVAC 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.