Pinpoint Test K: The Air Conditioning (A/C) is Always On - A/C Mode Always Commanded ON
Climate Control System
Pinpoint Tests
Pinpoint Test K: 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, 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 through the High Speed Controller Area Network (HS-CAN) bus to the PCM.
For gasoline engines, voltage is provided to the high-pressure cutoff switch. If the high-pressure cutoff switch is closed (pressure not excessive), voltage is sent to the A/C cycling switch. If the A/C cycling switch is closed (sufficient pressure) voltage is sent from the A/C cycling switch to the PCM.
For diesel engines, voltage is provided to the A/C cycling switch. If the A/C cycling switch is closed (sufficient pressure) voltage is sent from the A/C cycling switch to the dual-function pressure switch. If the dual-function pressure switch is closed (pressure not excessive), voltage is sent to the PCM.
For all engines, when the PCM receives voltage from the pressure switches, the PCM provides a ground for the A/C clutch relay. Voltage is provided to the A/C clutch relay switch. When the PCM energizes the relay by grounding it, voltage is supplied to the A/C clutch from the relay. Ground is supplied for the A/C clutch.
The A/C cycling switch is used for A/C compressor cycling. The A/C cycling switch is used by the PCM to turn off the A/C compressor when the refrigerant pressure is low enough to make the evaporator temperatures cold enough to freeze the condensation.
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 cycling switch
- A/C control relay
- A/C clutch air gap
PINPOINT TEST K: THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C MODE ALWAYS COMMANDED ON
NOTE: Before carrying out the following test, diagnose any HVAC, PCM or 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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K1 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQ) PCM PID WITH THE A/C OFF
- Start the engine.
- Enter the following diagnostic mode on the scan tool: AC_REQ PCM PID.
- With the engine running and A/C button OFF:
- (EMTC systems) Select PANEL mode.
- (DATC systems) Press the PANEL override button.
- Does the AC_REQ PCM PID read OFF?
Yes
GO to K4.
No
GO to K2.
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K2 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.
- With the engine running and A/C button OFF:
- (EMTC systems) Select PANEL mode.
- (DATC systems) Press the PANEL override button.
- Does the CC_AC HVAC PID read OFF?
Yes
GO to K4.
No
GO to K3.
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K3 CHECK THE HVAC MODULE CONNECTION
- Inspect the 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.
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K4 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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