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 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, when A/C is requested, a message is sent over the bus from the electronic automatic temperature control (EATC) module, through the instrument cluster, to the powertrain control module (PCM). The PCM receives input from the A/C cycling switch through circuit 883 (PK/LB). Voltage is provided to the A/C cycling switch through circuit 1040 (RD/BK)/348 (VT).
The PCM provides a ground for the A/C clutch relay coil through circuit 73 (OG/LB). The A/C clutch relay coil receives voltage through circuit 391 (RD/YE). Voltage for the A/C clutch relay switch is provided through circuit 1810 (LG/OG). When the relay is activated, voltage is supplied to the A/C clutch solenoid through circuit 321 (GY/WH). Ground is supplied for the A/C clutch through circuit 57 (BK).
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.
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.
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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. 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.
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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.
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. 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. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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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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