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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

NOTE: Before carrying out the following test, diagnose any PCM DTCs.

Normal Operation

Under normal operation, the function selector switch is supplied voltage. When any mode requiring A/C is selected, the function selector switch sends voltage to the A/C high-pressure switch. Voltage is then supplied from the A/C high-pressure switch to the A/C cycling switch. The voltage is then supplied from the A/C cycling switch to the PCM.

Voltage is supplied to the A/C clutch relay switch contact. When the relay is energized, voltage is sent to the A/C compressor clutch field coil. The A/C compressor clutch field coil is grounded.

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

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G1 CHECK THE AIR CONDITIONING CYCLING SWITCH (ACCS) PCM PID WITH THE A/C OFF


- Ignition ON.
- Turn the function selector switch to the OFF position.
- Enter the following diagnostic mode on the scan tool: ACCS PCM PID.
- Does the ACCS PCM PID read OFF?

Yes
GO to G5.

No
GO to G2.

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G2 CHECK CIRCUIT CH425 (GN/BU) FOR VOLTAGE


- Ignition OFF.
- Disconnect: PCM C175b.
- Ignition ON.
- Measure the voltage between ground and PCM C175b-15, circuit CH425 (GN/BU), harness side.




- Is any voltage present?

Yes
GO to G3.

No
GO to G5.

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G3 CHECK CIRCUIT CH423 (YE) FOR VOLTAGE


- Ignition OFF.
- Disconnect: A/C Cycling Switch C1081.
- Ignition ON.
- Measure the voltage between ground and A/C cycling switch C1081-1, circuit CH423 (YE), harness side.




- Is any voltage present?

Yes
GO to G4.

No
REPAIR circuit CH425 (GN/BU) for a short to voltage. TEST the system for normal operation.

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G4 CHECK CIRCUIT CH443 (GN/OG) FOR VOLTAGE


- Ignition OFF.
- Disconnect: A/C High Pressure Switch C1078.
- Ignition ON.
- Measure the voltage between ground and A/C cycling switch C1081-1, circuit CH443 (GN/OG), harness side.




- Is any voltage present?

Yes
CARRY OUT the function selector switch component test. If the switch tests OK, REPAIR circuit CH443 (GN/OG) for a short to voltage. TEST the system for normal operation.

No
REPAIR circuit CH423 (YE) for a short to voltage. TEST the system for normal operation.

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G5 CHECK MODULE CONNECTIONS


- Disconnect all PCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- Connect all PCM connectors 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. Concern may have been caused by a loose or corroded connector. TEST the system for normal operation.

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