Pinpoint Test O: The Air Conditioning (A/C) Is Inoperative
Climate Control System
Pinpoint Test O: The Air Conditioning (A/C) is Inoperative
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, when A/C is requested, the HVAC module sends an A/C request message over the Standard Corporate Protocol (SCP) bus to the Instrument Cluster (IC), then from the IC through the High Speed Controller Area Network (HS-CAN) bus to the PCM.
Voltage is provided to the A/C cycling switch. The PCM receives input from the A/C cycling switch when the A/C cycling switch is closed (sufficient pressure). The A/C cycling switch is used for A/C compressor cycling. The switch is used by the PCM to turn off the A/C compressor before the line pressures are low enough to drop the evaporator temperature excessively low and freeze the condensation.
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.
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 low refrigerant pressure from the A/C cycling switch.
- The PCM does not detect excessively high engine coolant temperature.
- The PCM does not detect an ambient air temperature too low.
- The PCM has not detected a Wide Open Throttle (WOT) condition.
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- A/C pressure transducer
- PCM
- A/C clutch relay
- HVAC module
- A/C cycling switch
- A/C compressor clutch field coil
- A/C clutch air gap
PINPOINT TEST O: THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTE: Before carrying out the following test, diagnose any PCM or Instrument Cluster (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 R-134a Manifold Gauge Set connected, compare the pressure readings of the manifold gauge set and the ACP_PRESS PID.
- Are the pressure values of the R-134a 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 AIR CONDITIONING SWITCH STATUS (AC_SEL_SW) HVAC PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: AC_SEL_SW HVAC PID.
- Press the panel and A/C manual override buttons on the HVAC module.
- Does the AC_SEL_SW HVAC PID read AC?
Yes
GO to O3.
No
GO to O13.
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O3 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.
- Press the panel and A/C manual override buttons on the HVAC module.
- Does the ACCS PCM PID read ON?
Yes
GO to O4.
No
GO to O5.
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O4 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.
- Does the WAC/ACCR PCM PID read ON?
Yes
GO to O8.
No
GO to O14.
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O5 CHECK A/C CYCLING SWITCH VOLTAGE
- Ignition OFF.
- Disconnect: A/C Cycling Switch C1081.
- Ignition ON.
- Measure the voltage between A/C cycling switch C1081-4, circuit 1040 (RD/BK)/348 (VT), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to O6.
No
VERIFY Central Junction Box (CJB) fuse 17 (10A) is OK. If OK, REPAIR circuit 1040 (RD/BK)/348 (VT) 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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O6 CHECK A/C CYCLING SWITCH
- Ignition OFF.
- Measure the resistance between the A/C cycling switch terminals.
- Is the resistance less than 21 ohms?
Yes
GO to O7.
No
INSTALL a new A/C cycling switch. TEST the system for normal operation.
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O7 CHECK CIRCUIT 883 (PK/LB) FOR AN OPEN
- Ignition OFF.
- Disconnect: PCM C175B.
- Measure the resistance between A/C cycling switch C1081-1, circuit 883 (PK/LB), harness side and PCM C175B-15, circuit 883 (PK/LB), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to O14.
No
REPAIR circuit 883 (PK/LB) for an open. TEST the system for normal operation.
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O8 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Start the engine.
- Measure the voltage between A/C compressor clutch field coil C100-1, circuit 321 (GY/WH), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to O9.
No
GO to O11.
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O9 CHECK THE GROUND AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Measure the voltage between A/C compressor clutch field coil C100-2, circuit 57 (BK), harness side and A/C compressor clutch field coil C100-1, circuit 321 (GY/WH), harness side.
- Is the voltage greater than 10 volts?
Yes
GO to O10.
No
REPAIR circuit 57 (BK). TEST the system for normal operation.
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O10 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 greater than 0.65 mm (0.026 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. REFER to Climate Control Service and Repair. TEST the system for normal operation.
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O11 CHECK CIRCUIT 1810 (LG/OG) FOR AN OPEN
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between A/C clutch relay socket pin 5, circuit 1810 (LG/OG) and ground.
- Is the voltage greater than 10 volts?
Yes
GO to O12.
No
VERIFY Battery Junction Box (BJB) fuse 11 (15A) is OK. If OK, REPAIR circuit 1810 (LG/OG) 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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O12 CHECK CIRCUIT 321 (GY/WH) FOR AN OPEN
- Ignition OFF.
- Measure the resistance between A/C clutch relay socket pin 3, circuit 321 (GY/WH) and A/C compressor clutch field coil C100-1, circuit 321 (GY/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
CARRY OUT the A/C clutch relay component test.
Refer to Compressor Clutch Relay for component testing.
If the relay tests OK, GO to O14.
No
REPAIR circuit 321 (GY/WH) for an open. TEST the system for normal operation.
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O13 CHECK THE HVAC 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. REFER to Climate Control Service and Repair. 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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O14 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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