Pinpoint Test I: The Air Conditioning (A/C) is Inoperative
Climate Control System
Pinpoint Tests
Pinpoint Test I: 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, when A/C is requested, the HVAC module sends an A/C request message over the Medium Speed Controller Area Network (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.
For gasoline engines, voltage is provided to the high-pressure cutoff switch. If the high-pressure cutoff switch is closed (pressure not excessive), voltage is sent to the A/C cycling switch. If the A/C cycling switch is closed (sufficient pressure) voltage is sent from the A/C cycling switch to the PCM.
For diesel engines, voltage is provided to the A/C cycling switch. If the A/C cycling switch is closed (sufficient pressure) voltage is sent from the A/C cycling switch to the dual-function pressure switch. If the dual-function pressure switch is closed (pressure not excessive), voltage is sent to the PCM.
For all engines, when the PCM receives voltage from the pressure switches, the PCM provides a ground for the A/C clutch relay. Voltage is provided to the A/C clutch relay switch. When the PCM energizes the relay by grounding it, voltage is supplied to the A/C clutch from the relay. Ground is supplied for the A/C clutch.
The A/C cycling switch is used for A/C compressor cycling. The A/C cycling switch is used by the PCM to turn off the A/C compressor when the refrigerant pressure is low enough to make the evaporator temperatures 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 low refrigerant pressure from the A/C cycling switch.
- For gasoline engines, the PCM does not detect excessively high refrigerant pressure from the high-pressure cutoff switch.
- For diesel engines, the PCM does not detect excessively high refrigerant pressure from the dual-function pressure switch.
- 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 - Electronic Manual Temperature Control (EMTC)
- HVAC module - Dual Automatic Temperature Control (DATC)
- A/C cycling switch
- For gasoline engines, high-pressure cutoff switch
- For diesel engines, dual-function pressure switch
- A/C compressor clutch field coil
- A/C clutch relay
- A/C clutch air gap
- Battery Junction Box (BJB)
PINPOINT TEST I: THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTICE: It is important to install relays in their correct position in the Battery Junction Box (BJB). Installing a relay incorrectly can cause wiring shorts or damage to modules. While carrying out diagnostics on BJB relays, have only one BJB relay removed at a time. Failure to follow these instructions can result in damage to the vehicle circuitry or to control modules.
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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I1 CHECK THE AIR CONDITIONING CLUTCH ALLOWED (ACCLT_ALW) PCM PID WITH THE A/C ON
- Start the engine.
- Enter the following diagnostic mode on the scan tool: ACCLT_ALW PCM PID.
- With the engine running:
- (EMTC systems) Select MAX A/C.
- (DATC systems) Press the PANEL and A/C override buttons.
- Does the ACCLT_ALW PCM PID read YES?
Yes
GO to I8.
No
GO to I2.
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I2 CHECK CIRCUIT CH421 (GY) FOR VOLTAGE
- Ignition OFF.
- Disconnect: (Gasoline Engines) PCM C175E.
- Disconnect: (Diesel Engines) PCM C1232e.
- Ignition ON.
- NOTE: Gasoline engines only.
- Measure the voltage between ground and PCM C175E-4, circuit CH421 (GY), harness side.
- NOTE: Diesel engines only.
- Measure the voltage between ground and PCM C1232e-36, circuit CH421 (GY), harness side.
- Is the voltage greater than 10 volts?
Yes
GO to I16.
No
GO to I3.
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I3 CHECK CIRCUIT CH432 (BU/GN) FOR VOLTAGE
- Ignition OFF.
- Disconnect: (Gasoline Engines) A/C Cycling Switch C1081.
- Disconnect: (Diesel Engines) Dual-Function Pressure Switch C1062.
- Ignition ON.
- NOTE: Gasoline engines only.
- Measure the voltage between ground and A/C cycling switch C1081-4, circuit CH432 (BU/GN), harness side.
- NOTE: Diesel engines only.
- Measure the voltage between ground and dual-function pressure switch C1062-4, circuit CH432 (BU/GN), harness side.
- Is the voltage greater than 10 volts?
Yes
For gasoline engines, GO to I7.
For diesel engines, GO to I4.
No
GO to I5.
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I4 CHECK CIRCUIT CH421 (GY) FOR AN OPEN
- Ignition OFF.
- Measure the resistance between dual-function pressure switch C1062-1, circuit CH421 (GY), harness side and PCM C1232e-36, circuit CH421 (GY), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new dual-function pressure switch. TEST the system for normal operation.
No
REPAIR circuit CH421 (GY) for an open. TEST the system for normal operation.
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I5 CHECK CIRCUIT CBB70 (YE/BU) OR CBB14 (VT/OG) FOR VOLTAGE
- Ignition OFF.
- Disconnect: (Gasoline Engines) High-Pressure Cutoff Switch C1078.
- Disconnect: (Diesel Engines) A/C Cycling Switch C1081.
- Ignition ON.
- NOTE: Gasoline engines only.
- Measure the voltage between ground and high-pressure cutoff switch C1078-3, circuit CBB14 (VT/OG), harness side.
- NOTE: Diesel engines only.
- Measure the voltage between ground and A/C cycling switch C1081-1, circuit CBB70 (YE/BU), harness side.
- Is the voltage greater than 10 volts?
Yes
For gasoline engines, GO to I6.
For diesel engines, GO to I7.
No
VERIFY BJB fuse 70 (10A) is OK. If OK, REPAIR circuit CBB70 (YE/BU) for an open. TEST the system for normal operation.
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I6 CHECK CIRCUIT CH432 (BU/GN) FOR AN OPEN
- Ignition OFF.
- Measure the resistance between high-pressure cutoff switch C1078-1, circuit CH432 (BU/GN), harness side and A/C cycling switch C1081-4, circuit CH432 (BU/GN), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new high-pressure cutoff switch. TEST the system for normal operation.
No
REPAIR circuit CH432 (BU/GN) for an open. TEST the system for normal operation.
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I7 CHECK THE A/C CYCLING SWITCH
- Ignition OFF.
- Measure the resistance between the A/C cycling switch terminals.
- Is the resistance less than 21 ohms?
Yes
For gasoline engines, REPAIR circuit CH421 (GY) for an open. TEST the system for normal operation.
For diesel engines, REPAIR circuit CH432 (BU/GN) for an open. TEST the system for normal operation.
No
INSTALL a new A/C cycling switch. TEST the system for normal operation.
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I8 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.
- With the engine running:
- (EMTC systems) Select MAX A/C.
- (DATC systems) Press the PANEL and A/C manual override buttons.
- Does the WAC/ACCR PCM PID read ON?
Yes
GO to I11.
No
GO to I9.
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I9 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.
- With the engine running:
- (EMTC systems) Select MAX A/C.
- (DATC systems) Press the PANEL and A/C manual override buttons.
- Does the AC_REQ PCM PID read ON?
Yes
GO to I16.
No
GO to I10.
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I10 CHECK THE AIR CONDITIONING SWITCH STATUS (CC_AC) HVAC PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: CC_AC HVAC PID.
- With the engine running:
- (EMTC systems) Select MAX A/C.
- (DATC systems) Press the PANEL and A/C manual override buttons.
- Does the CC_AC HVAC PID read ON?
Yes
GO to I16.
No
GO to I15.
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I11 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Start the engine.
- With the engine running:
- (EMTC systems) Select MAX A/C.
- (DATC systems) Press the PANEL and A/C manual override buttons.
- Measure the voltage between ground and A/C compressor clutch field coil C100-1, circuit CH401 (VT/WH), harness side.
- Is the voltage greater than 10 volts?
Yes
GO to I13.
No
CARRY OUT the A/C clutch relay component test.
If the relay tests OK, GO to I12.
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I12 CHECK THE A/C CLUTCH RELAY FOR VOLTAGE
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between ground and the A/C clutch relay socket.
- Is the voltage greater than 10 volts?
Yes
REPAIR circuit CH401 (VT/WH) for an open. TEST the system for normal operation.
No
VERIFY BJB fuse 30 (10A) is OK. If OK, INSTALL a new BJB. TEST the system for normal operation.
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I13 CHECK THE GROUND AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Measure the resistance between ground and A/C compressor clutch field coil C100-2, circuit GD124 (BK/VT), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to I14.
No
REPAIR circuit GD124 (BK/VT) for an open. TEST the system for normal operation.
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I14 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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I15 CHECK THE HVAC MODULE CONNECTION
- Carry out the HVAC Module Cold Boot Process.
- NOTE: DATC systems only.
- Carry out the HVAC Module - DATC On-Demand Self Test.
- Operate the system.
- Does the concern return?
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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I16 CHECK THE PCM 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 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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