Pinpoint Test L: The Air Conditioning (A/C) Is Inoperative
Climate Control System
Pinpoint Test L: The Air Conditioning (A/C) is Inoperative
Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information Electrical Diagrams.
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information Electrical Diagrams.
Normal Operation
When the A/C is requested, the Front Controls Interface Module (FCIM) sends the button press message over the Infotainment Controller Area Network (I-CAN) to the Instrument Panel Cluster (IPC) module. The IPC (Instrument Panel Cluster) module then sends the button press message to Body Control Module (BCM) over the High Speed Controller Area Network (HS-CAN). The BCM (Body Control Module) then sends the button press message to the HVAC module over the Medium Speed Controller Area Network (MS-CAN). Lastly the HVAC module sends an A/C 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 request through the HS-CAN (High Speed Controller Area Network) to the PCM.
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 compressor clutch field coil from the relay. Ground is supplied for the A/C compressor clutch field coil.
The evaporator discharge air temperature sensor is used for A/C compressor cycling. An accurate evaporator temperature is critical for compressor engagement. The PCM uses the temperature measurement to turn the A/C compressor off before the evaporator temperatures are cold enough to freeze the condensation on the evaporator core.
When an A/C request is received by the PCM, the A/C compressor clutch only engages 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
- A/C system discharged/low charge
- PCM
- HVAC module
- FCIM (Front Controls Interface Module)
- Evaporator discharge air temperature sensor
- A/C pressure transducer
- A/C compressor clutch field coil
- A/C clutch relay
- A/C compressor clutch air gap
PINPOINT TEST L : THE AIR CONDITIONING (A/C) IS INOPERATIVE
L1 CHECK THE A/C SYSTEM PRESSURE
- Ignition OFF.
- With the R-134a manifold gauge set connected, check the A/C system pressure.
Is the A/C system pressure above 290 kPa (42 psi)?
Yes
GO to L2.
No
CHECK the A/C system for leaks. REFER to Fluorescent Dye Leak Detection Fluorescent Dye Leak Detection or Electronic Leak Detection . RECHARGE the A/C system. REFER to Air Conditioning (A/C) System Recovery, Evacuation and Charging Air Conditioning (A/C) System Recovery, Evacuation and Charging. TEST the system for normal operation.
L2 CHECK THE A/C PRESSURE SENSOR (ACP_PRESS) PCM PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: PCM DataLogger.
- With the R-134a 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 L3.
No
INSTALL a new A/C pressure transducer. TEST the system for normal operation.
L3 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC PID
- Allow the vehicle exterior and interior to stabilize to the ambient temperature.
- Enter the following diagnostic mode on the scan tool: HVAC DataLogger.
- Monitor the EVAP_TEMP HVAC PID
Does the EVAP_TEMP HVAC PID read similar to the ambient temperature?
Yes
GO to L4.
No
INSTALL a new evaporator discharge air temperature sensor. TEST the system for normal operation.
L4 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: FCIM (Front Controls Interface Module) DataLogger.
- Monitor the 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 L5.
No
INSTALL a new FCIM (Front Controls Interface Module). TEST the system for normal operation.
L5 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQ) PCM PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: PCM DataLogger.
- Select PANEL press the A/C button (indicator on) on the HVAC controls.
- Monitor the AC_REQ PCM PID
Does the AC_REQ PCM PID read ON?
Yes
GO to L6.
No
GO to L16.
L6 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: PCM DataLogger.
- Select PANEL press the A/C button (indicator on) on the HVAC controls.
- Monitor the ACC_CMD PCM PID
Does the ACC_CMD PCM PID read ON?
Yes
GO to L7.
No
GO to L17.
L7 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY COIL
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between ground and the A/C clutch relay socket, circuit CBB70 (YE/BU).
Is the voltage greater than 10 volts?
Yes
GO to L8.
No
VERIFY Battery Junction Box (BJB) fuse 70 (10A) is OK. If OK, REPAIR circuit CBB70 (YE/BU) 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 Electrical Diagrams.
L8 CHECK THE A/C CLUTCH RELAY
- Start the engine.
- Select PANEL and press the A/C button (indicator on) on the HVAC controls.
- With the engine running, connect a 12-volt test light between A/C clutch relay socket, circuit CBB70 (YE/BU) and A/C clutch relay socket, circuit CH302 (WH/BN).
Does the test light illuminate?
Yes
GO to L11.
No
GO to L9.
L9 CHECK THE A/C CLUTCH RELAY COIL SWITCHED GROUND CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: PCM C175B (for 3.5L/3.7L engine) or C1381B (for 2.0L engine).
- Ignition ON.
- For the 3.5L or 3.7L engine, measure the voltage between ground and PCM C175B-12, circuit CH302 (WH/BN), harness side.
- For the 2.0L engine, measure the voltage between ground and PCM C1381B-10, circuit CH302 (WH/BN), harness side.
Is any voltage present?
Yes
REPAIR circuit CH302 (WH/BN) for a short to voltage. TEST the system for normal operation.
No
GO to L10.
L10 CHECK THE A/C CLUTCH RELAY COIL SWITCHED GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Measure the resistance between A/C clutch relay socket, circuit CH302 (WH/BN) and PCM C175B-12, circuit CH302 (WH/BN), harness side.
- Measure the resistance between A/C clutch relay socket, circuit CH302 (WH/BN) and PCM C1381B-10, circuit CH302 (WH/BN), harness side.
Is the resistance less than 5 ohms?
Yes
GO to L17.
No
REPAIR circuit CH302 (WH/BN) for an open. TEST the system for normal operation.
L11 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY SWITCH CONTACTS
- Measure the voltage between A/C clutch relay socket, circuit SBB62 (BN/RD) and ground.
Is the voltage greater than 10 volts?
Yes
GO to L12.
No
VERIFY Battery Junction Box (BJB) fuse 62 (10A) is OK. If OK, REPAIR circuit SBB62 (BN/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 Electrical Diagrams.
L12 CHECK THE A/C COMPRESSOR CLUTCH FIELD COIL VOLTAGE CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- 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 less than 5 ohms?
Yes
GO to L13.
No
REPAIR circuit CH401 (VT/WH) for an open. TEST the system for normal operation.
L13 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Connect: A/C Clutch Relay.
- Start the engine.
- Select PANEL and press the A/C button (indicator on) on the HVAC controls.
- 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 L14.
No
INSTALL a new A/C clutch relay. TEST the system for normal operation.
L14 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 L15.
No
REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.
L15 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
INSTALL a new A/C compressor.
No
INSTALL a new A/C compressor clutch field coil. TEST the system for normal operation.
L16 CHECK THE HVAC MODULE CONNECTION
- Inspect the HVAC module component and harness side connectors for:
- corrosion
- damaged pins
- pushed-out terminals
- Connect and correctly seat all the HVAC module connectors.
- Clear the DTCs.
- Enter the following diagnostic mode on the scan tool: Self-Test- HVAC Module.
- 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 L17.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. TEST the system for normal operation.
L17 CHECK THE PCM CONNECTION
- Disconnect all the PCM connectors.
- Inspect the PCM component and harness side connectors for:
- corrosion
- damaged pins
- pushed-out terminals
- Connect and correctly seat all the PCM connectors.
- Clear the DTCs.
- Enter the following diagnostic mode on the scan tool: Self-Test- PCM.
- 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.