Pinpoint Test M: The Air Conditioning (A/C) Is Always On - A/C Mode Always Commanded On
Climate Control System
Pinpoint Tests
Pinpoint Test M: 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, a message is sent from the HVAC module over the Medium Speed Controller Area Network (MS-CAN) bus to the PCM. Ignition voltage is provided to the A/C clutch relay switch through circuit SBB24 (VT/RD). When the PCM energizes the relay, ignition voltage is supplied to the A/C clutch through circuit CH421 (GY). Ground is supplied for the A/C clutch through circuit GD120 (BK/GN).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM
- HVAC module - Dual Automatic Temperature Control (DATC)
- HVAC module - Electronic Manual Temperature Control (EMTC)
- A/C evaporator discharge temperature sensor
- A/C pressure transducer
- A/C control relay
- A/C clutch air gap
PINPOINT TEST M: THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C MODE ALWAYS COMMANDED ON
NOTE: Before carrying out the following test, diagnose any PCM or Instrument Cluster (IC) DTCs.
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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M1 CHECK THE ACCS PCM PID WITH THE A/C OFF
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: ACCS PCM PID.
- Does the ACCS PCM PID read ON?
Yes
GO to M2.
No
GO to M4.
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M2 CHECK THE AIR CONDITIONING SWITCH STATUS (AC_SEL_SW) HVAC PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: AC_SEL_SW HVAC PID.
- Does the AC_SEL_SW HVAC PID read PRESSED?
Yes
GO to M3.
No
GO to M4.
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M3 CHECK THE MODULE CONNECTION
- Carry out the HVAC Module Cold Boot Process. HVAC Module Cold Boot Process
- NOTE: DATC systems only.
- Carry out the HVAC Module - Dual Automatic Temperature Control (DATC) On-Demand Self Test. Alternate Diagnostic Methods - HVAC Module - Dual Automatic Temperature Control (DATC) Only
- 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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M4 CHECK THE PCM CONNECTION
- Clear the DTCs.
- Disconnect all of the PCM connectors.
- Check for:
- corrosion.
- pushed-out connectors.
- incorrectly seated connector.
- Connect and correctly seat all of 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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