Pinpoint Test I: The Air Conditioning (A/C) is Inoperative
Climate Control System
Pinpoint Test I: The Air Conditioning (A/C) is Inoperative
Refer to Wiring Diagram Set 55 (Fusion/Milan/MKZ, Fusion Hybrid, Milan Hybrid, MKZ Hybrid), Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, for vehicles equipped with navigation, when the 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.
For vehicles equipped with navigation, 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.
When an A/C request is received from the HVAC module, an A/C demand message is sent from the PCM over the HS-CAN bus to the Air Conditioning Compressor Module (ACCM) if all of the following conditions are met:
- The PCM does not detect excessively high or low refrigerant pressure from the A/C pressure transducer.
- The PCM does not detect excessively high engine coolant temperature.
- The PCM does not detect an ambient air temperature below -1°C (30°F).
- The PCM has not detected a Wide Open Throttle (WOT) condition.
- The HVAC module does not detect an evaporator discharge air temperature below 2°C (36°F).
When the ACCM receives the A/C demand message, it will engage. Instead of cycling ON and OFF like a traditional A/C compressor, the PCM monitors the evaporator discharge temperature from the HVAC module to raise or lower the electric A/C compressor speed as required.
This pinpoint test is intended to diagnose the following:
- HVAC module
- PCM
- FCIM
- ACM
- Electric A/C compressor
- A/C evaporator discharge temperature sensor
- A/C pressure transducer
PINPOINT TEST I: THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTE: Diagnose any PCM, HVAC module or ACCM DTCs before carrying out the following pinpoint test.
NOTE: Before carrying out the following test, check that the A/C system pressure is above 290 kPa (42 psi). If the pressure is below 290 kPa (42 psi), refer to Climate Control System - General Information and Diagnostics Refrigerant System Tests.
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I1 CHECK THE A/C PRESSURE SENSOR (ACP_PRESS) PCM PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: ACP_PRESS PCM PID.
- With the manifold gauge set connected, compare the pressure readings of the manifold gauge set and the ACP_PRESS PID.
- Are the pressure values of the manifold gauge set and the ACP_PRESS PID similar?
Yes
GO to I2.
No
INSTALL a new A/C pressure transducer. TEST the system for normal operation.
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I2 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC PID
- Allow the vehicle exterior and interior to stabilize to an ambient temperature.
- Enter the following diagnostic mode on the scan tool: EVAP_TEMP HVAC PID.
- Does the EVAP_TEMP HVAC PID read similar to the ambient temperature?
Yes
For vehicles not equipped with navigation, GO to I3.
For vehicles equipped with navigation, GO to I4.
No
INSTALL a new A/C evaporator discharge temperature sensor. TEST the system for normal operation.
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I3 CHECK THE (A/C) SWITCH (CC_SW_AC) HVAC PID WITH THE A/C ON
- Start the engine.
- Enter the following diagnostic mode on the scan tool: CC_SW_AC HVAC PID.
- Select PANEL and press the A/C button (indicator OFF).
- Does the CC_SW_AC HVAC PID read Active?
Yes
GO to I5.
No
GO to I6.
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I4 CHECK THE (A/C) SWITCH (CC_SW_AC) FCIM PID WITH THE A/C ON
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 U0256:00 is not present, install a new FCIM. Test the system for normal operation. If DTC U0256:00 is present, diagnose the DTC first.
- Start the engine.
- Enter the following diagnostic mode on the scan tool: CC_SW_AC FCIM PID.
- Select PANEL and press the A/C button (indicator on).
- Does the CC_SW_AC FCIM PID read Active?
Yes
GO to I5.
No
INSTALL a new FCIM. REFER to Information and Entertainment Systems Service and Repair. TEST the system for normal operation.
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I5 CHECK THE AIR CONDITIONING COMPRESSOR COMMANDED STATE (ACC_CMD) PCM PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: ACC_CMD PCM PID.
- Does the ACC_CMD PCM PID read ON?
Yes
GO to I8.
No
GO to I7.
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I6 CHECK THE 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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I7 CHECK THE PCM CONNECTION
- Clear the DTCs.
- Disconnect all of the PCM connectors.
- Check for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- 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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I8 CHECK ACCM OPERATING CONDITIONS
- Make sure the following conditions are met:
- The PCM does not detect excessively high or low refrigerant pressure from the A/C pressure transducer.
- The PCM does not detect excessively high engine coolant temperature.
- The PCM does not detect an ambient air temperature below -1°C (30°F).
- The PCM has not detected a Wide Open Throttle (WOT) condition.
- The HVAC module does not detect an evaporator discharge air temperature below 2°C (36°F).
- Start the engine.
- Select PANEL and press the A/C button (indicator on).
- Does the A/C operate?
Yes
The system is operating correctly at this time. The concern may have been caused by attempting to operate the A/C outside of operating conditions.
No
INSTALL a new electric A/C compressor. REFER to Climate Control Service and Repair. TEST the system for normal operation.
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