Pinpoint Test O: The Air Conditioning (A/C) Is Inoperative
Climate Control System
Pinpoint Tests
Pinpoint Test O: 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, for vehicles equipped with navigation, when 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 bus to the Instrument Cluster (IC), then from the IC through the High Speed Controller Area Network (HS-CAN) bus to the PCM. When MAX A/C is selected on the touch screen, the Audio Control Module (ACM) sends a message over the MS-CAN bus to the HVAC module that MAX A/C has been selected.
For vehicles not equipped with navigation, when A/C is requested, a message is sent from the HVAC module over the MS-CAN bus to the IC, then from the IC through the HS-CAN bus to the PCM.
Ignition voltage is provided to the A/C clutch relay switch through circuit SBB30 (BN/RD). When the PCM energizes the relay, ignition voltage is supplied to the A/C clutch through circuit CH401 (VT/WH). Ground is supplied for the A/C clutch through circuit GD123 (BK/GY).
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
- ACM
- 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 O: THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTE: Before carrying out the following test, diagnose any HVAC, PCM or IC 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.
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O1 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 O2.
No
INSTALL a new A/C pressure transducer. TEST the system for normal operation.
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O2 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC PID
- Allow the vehicle exterior and interior to stabilize to an ambient temperature above 16°C (60°F).
- 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 vehicles with navigation, GO to O4.
For vehicles without navigation, GO to O3.
No
INSTALL a new A/C evaporator temperature sensor. TEST the system for normal operation.
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O3 CHECK THE (A/C) SWITCH (CC_SW_AC) HVAC PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: CC_SW_AC HVAC PID.
- Select PANEL press the A/C button (indicator on) on the HVAC module.
- Does the CC_SW_AC HVAC PID read Active?
Yes
GO to O6.
No
GO to O12.
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O4 CHECK THE A/C INDICATOR WITH THE A/C ON
NOTE: Before carrying out this test step, be sure all other FCIM button functions are operational. If all other buttons operate correctly, continue with this test step. If multiple buttons are inoperative and DTC U0256:87 is not present, install a new FCIM. Test the system for normal operation. If DTC U0256:87 is present, diagnose the DTC first.
- Select PANEL press the A/C button on the HVAC module.
- Does the A/C indicator illuminate when the A/C button is pressed?
Yes
GO to O6.
No
GO to O5.
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O5 CHECK THE MAX A/C OPERATION
NOTE: Before carrying out this test step, be sure all other ACM touch screen functions are operational. If all other touch screen functions operate correctly, continue with this test step. If multiple touch screen functions are inoperative and DTC U0256:87 is not present, install a new ACM. Test the system for normal operation. If DTC U0256:87 is present, diagnose the DTC first.
- Select MAX A/C on the navigation screen.
- Does the A/C operate when MAX A/C is selected?
Yes
INSTALL a new FCIM. TEST the system for normal operation.
No
GO to O12.
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O6 CHECK THE AIR CONDITIONING COMPRESSOR COMMANDED STATE (AC_CMD) PCM PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: AC_CMD PCM PID.
- Does the AC_CMD PCM PID read ON?
Yes
GO to O7.
No
GO to O13.
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O7 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Ignition ON.
- 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 O8.
No
GO to O10.
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O8 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 O9.
No
REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
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O9 CHECK THE A/C COMPRESSOR CLUTCH AIR GAP
- Measure the A/C compressor clutch air gap at 3 equally spaced locations between the clutch hub and the A/C compressor clutch pulley.
- Is the A/C compressor clutch air gap average greater than 0.65 mm (0.030 in)?
Yes
ADJUST the A/C compressor clutch gap. REFER to Air Conditioning (A/C) Clutch Air Gap Adjustment Adjustments. TEST the system for normal operation.
No
INSTALL a new A/C compressor clutch field coil. TEST the system for normal operation.
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O10 CHECK THE A/C CLUTCH RELAY FOR VOLTAGE
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between the A/C clutch relay socket, circuit SBB30 (BN/RD) and ground.
- Is the voltage greater than 10 volts?
Yes
GO to O11.
No
VERIFY Battery Junction Box (BJB) fuse 30 (10A) is OK. If OK, REPAIR circuit SBB30 (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. Diagrams By Number
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O11 CHECK CIRCUIT CH401 (VT/WH) FOR AN OPEN
- Ignition OFF.
- Measure the resistance between the 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
CARRY OUT the A/C clutch relay component test. If the relay tests OK, GO to O13.
No
REPAIR circuit CH401 (VT/WH) for an open. TEST the system for normal operation.
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O12 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 O13.
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.
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O13 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.
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