Pinpoint Test G: The Air Conditioning (A/C) Is Always On - A/C Mode Always Commanded ON
Climate Control System
Pinpoint Tests
Pinpoint Test G: 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 23 for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 24 for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 25 for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 26 for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, voltage is provided to the function selector switch through circuit CBP37 (WH). When A/C is requested, voltage is sent from the function selector switch to the A/C cycling switch through circuit CH434 (GY/YE). Voltage is sent from the A/C cycling switch to the dual-function pressure switch (diesel engine) or the A/C high pressure switch (gasoline engine) through circuit CH423 (YE). Voltage is sent from the dual-function pressure switch (diesel engine) or the A/C high pressure switch (gasoline engine) to the PCM through circuit CH419 (BU).
The PCM provides a ground for the A/C clutch relay coil through circuit CH302 (WH/BN). The A/C clutch relay coil receives ignition voltage through circuit CBB77 (WH). Battery voltage for the A/C clutch relay switch is provided through circuit SBB29 (GY/RD). When the relay is energized, voltage is supplied to the A/C clutch field coil through circuit (gasoline engine) CH401 (WH/VT) or (diesel engine) CH401 (WH/VT)/321 (GY/WH). Ground is supplied for the A/C clutch through circuit (gasoline engine) GD123 (BK/GY) or (diesel engine) 57 (BK).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM
- Function selector switch
- A/C control relay
- A/C clutch air gap
PINPOINT TEST G: THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C MODE ALWAYS COMMANDED ON
NOTE: Before carrying out the following test, diagnose any PCM DTCs.
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G1 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQ) PCM PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: AC_REQ PCM PID.
- Place the function selector switch to the OFF position.
- Does the AC_REQ PCM PID read YES?
Yes
GO to G2.
No
GO to G4.
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G2 CHECK FOR VOLTAGE AT THE A/C CYCLING SWITCH
- Ignition OFF.
- Disconnect: A/C Cycling Switch C130.
- Ignition ON.
- Measure the voltage between A/C cycling switch C130-1, circuit CH434 (GY/YE), harness side and ground.
- Is any voltage present?
Yes
GO to G3.
No
GO to G4.
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G3 CHECK CIRCUIT CH434 (GY/YE) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Function Selector Switch C294a.
- Ignition ON.
- Measure the voltage between A/C cycling switch C130-1, circuit CH434 (GY/YE), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit CH434 (GY/YE) for a short to voltage. TEST the system for normal operation.
No
INSTALL a new function selector switch. TEST the system for normal operation.
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G4 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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