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

Climate Control System

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 Electrical Diagrams.

Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information Electrical Diagrams.

Normal Operation

Under normal operation, when A/C is requested, the HVAC module sends an A/C request message over the Medium Speed Controller Area Network (MS-CAN) bus to the Instrument Cluster (IC), then from the IC (Instrument Cluster) through the High Speed Controller Area Network (HS-CAN) bus to the PCM.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- PCM

- HVAC module

- 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

NOTICE: It is important to install relays in their correct position in the Battery Junction Box (BJB). Installing a relay incorrectly can cause wiring shorts or damage to modules. While carrying out diagnostics on BJB (Battery Junction Box) relays, have only one BJB (Battery Junction Box) relay removed at a time. Failure to follow these instructions can result in damage to the vehicle circuitry or to control modules.

NOTE: Before carrying out the following test, diagnose any HVAC, PCM or IC (Instrument Cluster) DTCs.

M1 CHECK THE AIR CONDITIONING COMPRESSOR CYCLING SWITCH (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
For Electronic Manual Temperature Control (EMTC) systems, GO to M3.

For Dual Automatic Temperature Control (DATC) systems, GO to M2.

M2 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 M3.

No
GO to M4.

M3 CHECK THE HVAC MODULE CONNECTION

- Inspect the HVAC module connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.


- Connect and correctly seat all the HVAC module connectors.

- Clear the DTCs.

- Operate the system and verify the concern is still present.

Is the concern still present?

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.

M4 CHECK THE PCM CONNECTION

- Disconnect all the PCM connectors.

- Inspect the module connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.


- Connect and correctly seat all the PCM connectors.

- Clear the DTCs.

- Operate the system 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. The concern may have been caused by a loose or corroded connector.