Pinpoint Test O: The Air Conditioning (A/C) Is Always On - A/C Mode Always Commanded ON
Climate Control System
Pinpoint Tests
Pinpoint Test O: The Air Conditioning (A/C) is Always On - A/C Mode Always Commanded ON
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 in Electronic Automatic Temperature Control (EATC) or Dual Automatic Temperature Control (DATC) systems, a message is sent 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; or a voltage is sent to the IC through circuit CH434 (GY/YE), then a message is sent from the IC through the HS-CAN bus to the PCM Electronic Manual Temperature Control (EMTC) systems.
Ignition voltage for the A/C clutch relay switch is provided through circuit SBB25 (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 GD121 (BK/YE).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM
- HVAC module - EATC
- HVAC module - DATC
- HVAC module - EMTC
PINPOINT TEST O: THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C MODE ALWAYS COMMANDED ON
NOTE: When disconnecting and reconnecting the pressure transducer electrical connector, make sure that the connector-locking device is in place and that the locking device and connector are correctly and fully seated.
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O1 CHECK THE AIR CONDITIONING COMPRESSOR CYCLING SWITCH (ACCS) PCM PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: ACCS PCM PID.
- Press the OFF manual override buttons on the HVAC module - DATC and HVAC module - EATC or select OFF on the HVAC module - EMTC.
- Does the ACCS PCM PID read ON?
Yes
DATC/EATC, GO to O2.
EMTC, GO to O3.
No
GO to O6.
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O2 CHECK THE AIR CONDITIONING SWITCH STATUS (CC_AC) HVAC PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: CC_AC HVAC PID.
- Does the CC_AC HVAC PID read DEPRESSED?
Yes
GO to O5.
No
GO to O6.
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O3 CHECK EMTC A/C REQUEST OUTPUT
- Ignition OFF.
- Disconnect: IC C220.
- Ignition ON.
- Select the OFF position on the HVAC module - EMTC.
- Measure the resistance between IC C220-23, circuit CH434 (GY/YE), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to O4.
No
GO to O6.
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O4 CHECK CIRCUIT CH434 (GY/YE) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: HVAC module - EMTC C2357a.
- Ignition ON.
- Measure the resistance between IC C220-23, circuit CH434 (GY/YE), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to O5.
No
REPAIR circuit CH434 (GY/YE) for a short to ground. TEST the system for normal operation.
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O5 CHECK THE MODULE CONNECTION
- Carry out the HVAC Module Cold Boot Process. HVAC Module Cold Boot Process
- NOTE: DATC/EATC systems only.
- Carry out the HVAC Module - Electronic Automatic Temperature Control (EATC) and HVAC Module - Dual Automatic Temperature Control (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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O6 CHECK THE PCM CONNECTION
- Clear the DTCs.
- Disconnect all the PCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- incorrectly seated connector.
- Connect and correctly seat all the PCM connectors.
- Operate the system.
- Does the concern return?
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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