Pinpoint Test Q: The Air Conditioning (A/C) Is Always On - A/C Mode Always Commanded On
Climate Control System
Pinpoint Tests
Pinpoint Test Q: 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, for vehicles equipped with navigation, when A/C button is pressed, a message is sent from the Front Controls Interface Module (FCIM) over the Medium Speed Controller Area Network (MS-CAN) bus to the HVAC module. The HVAC module then sends an A/C request message over the 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. When MAX A/C is selected on the touch screen, the Audio Control Module (ACM) sends a message over the MS-CAN bus to the HVAC module that MAX A/C has been selected.
For vehicles not equipped with navigation, when A/C is requested, a message is sent from the HVAC module over the MS-CAN bus to the IC, then from the IC through the HS-CAN bus to the PCM.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM
- HVAC module
PINPOINT TEST Q: 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.
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Q1 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQ) PCM PID WITH THE A/C OFF
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: AC_REQ PCM PID.
- Select PANEL press the A/C button (indicator off) on the HVAC module.
- Does the AC_REQ PCM PID read YES?
Yes
For vehicles with navigation, GO to Q3.
For vehicles without navigation, GO to Q2.
No
GO to Q6.
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Q2 CHECK THE AIR CONDITIONING SWITCH STATUS (CC_SW_AC) HVAC PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: CC_SW_AC HVAC PID.
- Select PANEL press the A/C button (indicator off) on the HVAC module.
- Does the CC_SW_AC HVAC PID read Inactive?
Yes
GO to Q6.
No
GO to Q5.
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Q3 CHECK THE A/C INDICATOR WITH THE A/C OFF
NOTE: Before carrying out this test step, be sure all other FCIM button functions are operational. If all other buttons operate correctly, continue with this test step. If multiple buttons are inoperative and DTC U0256:87 is not present, install a new FCIM. Test the system for normal operation. If DTC U0256:87 is present, diagnose the DTC first.
- Select PANEL press the A/C button (indicator off) on the HVAC module.
- Does the A/C indicator turn off when the A/C button is pressed?
Yes
GO to Q5.
No
GO to Q4.
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Q4 CHECK THE MAX A/C OPERATION
NOTE: Before carrying out this test step, be sure all other ACM touch screen functions are operational. If all other touch screen functions operate correctly, continue with this test step. If multiple touch screen functions are inoperative and DTC U0256:87 is not present, install a new ACM. Test the system for normal operation. If DTC U0256:87 is present, diagnose the DTC first.
- Select MAX A/C on the navigation screen.
- Does the A/C turn off when MAX A/C is selected?
Yes
INSTALL a new FCIM. TEST the system for normal operation.
No
GO to Q5.
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Q5 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.
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Q6 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.
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