Pinpoint Test N: The Air Conditioning (A/C) Is Always On - A/C Mode Always Commanded ON

Climate Control System

Pinpoint Tests

Pinpoint Test N: 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 over the bus to the PCM (Dual Automatic Temperature Control (DATC) systems) or sends voltage to the PCM through circuit CH443 (GN/OG) (manual climate control systems). The PCM receives input from the A/C cycling switch through circuit CH423 (YE) and from the A/C pressure cutoff switch through circuit CH423 (YE). Ground is provided to the A/C cycling switch and A/C pressure cutoff switch through circuit GD113 (BK/YE).

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 CBB40 (YE/GN). Ignition voltage for the A/C clutch relay switch is provided through circuit SBB35 (BU/RD). When the relay is activated, ignition voltage is supplied to the A/C clutch solenoid through circuit CH401 (VT/WH). Ground is supplied for the A/C clutch through circuit GD120 (BK).

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM
- (DATC systems) HVAC module - DATC
- (Manual climate control systems) Function selector switch



PINPOINT TEST N: THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C MODE ALWAYS COMMANDED ON

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N1 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.
- Place the function selector switch to the OFF position or press the OFF manual override button on the HVAC module - DATC.
- Does the ACCS PCM PID read OFF?

Yes
GO to N6.

No
GO to N4.

For manual climate control systems, GO to N2.

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N2 CHECK CIRCUIT CH443 (GN/OG) FOR A SHORT TO VOLTAGE


- Ignition OFF.
- Disconnect: Climate Control Assembly C294b and C294c.
- Disconnect: PCM C175b.
- Ignition ON.
- Measure the voltage between ground and PCM 175b-15, circuit CH443 (GN/OG), harness side.




- Is any voltage present?

Yes
REPAIR circuit CH443 (GN/OG) for a short to voltage. TEST the system for normal operation.

No
GO to N3.

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N3 CHECK THE FUNCTION SELECTOR SWITCH


- Ignition OFF.
- Carry out the function selector switch component test. Switch - Function Selector
- Does the function selector switch test good?

Yes
GO to N5.

No
INSTALL a new function selector switch. TEST the system for normal operation.

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N4 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.
- Select PANEL mode on the HVAC module and make sure the A/C button and indicator are OFF.
- Does the AC_SEL_SW HVAC PID read Not Pressed?

Yes
GO to N6.

No
GO to N5.

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N5 CHECK MODULE CONNECTION


- Carry out the HVAC Module - Dual Automatic Temperature Control (DATC) Cold Boot Process. Alternate Diagnostic Methods - HVAC Module - Dual Automatic Temperature Control
- Carry out the HVAC Module - Dual Automatic Temperature Control (DATC) On-Demand Self-Test. Alternate Diagnostic Methods - HVAC Module - Dual Automatic Temperature Control
- Operate the system.
- Does the concern return?

Yes
INSTALL a new HVAC module - DATC. 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.

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N6 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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