Pinpoint Test F: The Air Conditioning (A/C) Is Inoperative
Climate Control System
Pinpoint Tests
Pinpoint Test F: The Air Conditioning (A/C) Is Inoperative
Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, when A/C is requested, a ground signal is sent from the HVAC module to the Smart Junction Box (SJB) through circuit 1397 (GY/RD). The SJB then transmits an A/C request message through the High Speed Controller Area Network (HS-CAN) bus to the PCM.
4.0L only
Voltage is provided to the A/C cycling switch through circuit 391 (RD/YE). If the A/C cycling switch is closed (sufficient pressure) voltage is sent from the A/C cycling switch to the PCM (4.0L) through circuit 198 (DG/OG)/420 (DB/YE). When the PCM receives voltage from the pressure switch and the A/C pressure transducer does not indicate excessive pressure, the PCM provides a ground for the A/C clutch relay through circuit 321 (GY/WH).
4.6L and 5.4L only
Voltage is provided to the A/C cycling switch through circuit 391 (RD/YE). 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 (4.6L and 5.4L) through circuit 198 (DG/OG). If the dual-function pressure switch (4.6L and 5.4L) is closed (pressure not excessive), voltage is sent to the PCM through circuit 420 (DB/YE). When the PCM receives voltage from the pressure switches, the PCM provides a ground for the A/C clutch relay through circuit 321 (GY/WH).
When the relay is activated, ignition voltage is supplied to the A/C clutch solenoid through circuit 883 (PK/LB). Ground is supplied for the A/C clutch through circuit 1205 (BK).
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- PCM
- HVAC module
- A/C cycling switch
- Dual-function pressure switch
- A/C compressor clutch field coil
- A/C control relay
- A/C clutch air gap
PINPOINT TEST F: THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTICE: It is important to install relays in their correct position in the Bussed Electrical Center (BEC). Installing a relay incorrectly may cause wiring shorts or damage to modules. While carrying out diagnostics on BEC relays, have only one BEC relay removed at a time. Failure to follow these instructions may result in damage to the vehicle circuitry or to control modules.
NOTE: Some PCM DTCs may inhibit A/C operation. If any PCM DTCs are retrieved, diagnose those first. Refer to the PCM DTC Chart. PCM DTC Chart
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 Fluorescent Dye Leak Detection Fluorescent Dye Leak Detection.
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F1 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQST) GEM PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: AC_REQST GEM PID.
- With the engine running, select PANEL mode and press the A/C button on the HVAC module.
- Does the AC_REQST GEM PID read ON?
Yes
GO to F5.
No
GO to F2.
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F2 CHECK THE A/C SIGNAL WITH THE A/C ON
- Ignition OFF.
- Disconnect: SJB C2280b.
- Disconnect: SJB C2280a.
- Ignition ON.
- Select PANEL mode and press the A/C button on the HVAC module.
- Measure the voltage between SJB C2280b-29, circuit 1397 (GY/RD), harness side and SJB C2280a-36, circuit 1044 (WH/YE), harness side.
- Is the voltage greater than 10 volts?
Yes
GO to F18.
No
GO to F3.
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F3 CHECK CIRCUIT 1397 (GY/RD) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: HVAC Module C294a.
- Ignition ON.
- Measure the voltage between HVAC module C294a-3, circuit 1397 (GY/RD), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit 1397 (GY/RD) for a short to voltage. TEST the system for normal operation.
No
GO to F4.
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F4 CHECK CIRCUIT 1397 (GY/RD) FOR AN OPEN
- Ignition OFF.
- Disconnect: HVAC Module C294a.
- Measure the resistance between HVAC module C294a-3, circuit 1397 (GY/RD), harness side and SJB C2280b-29, circuit 1397 (GY/RD), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to F19.
No
REPAIR circuit 1397 (GY/RD) for an open. TEST the system for normal operation.
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F5 CHECK THE AIR CONDITIONING COMPRESSOR CYCLING SWITCH (ACCS) PCM PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: ACCS PCM PID.
- Select PANEL mode and press the A/C button on the HVAC module.
- Does the ACCS PCM PID read ON?
Yes
For 4.0L, GO to F6. For 4.6L and 5.4L, GO to F12.
No
GO to F7.
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F6 CHECK THE A/C PRESSURE SENSOR (ACP_PRESS) PCM PID
- Enter the following diagnostic mode on the scan tool: A/C Pressure PCM PID.
- With the manifold gauge set connected, compare the pressure readings of the manifold gauge set and the ACP_PRESS PCM PID.
- Are the pressure values of the manifold gauge set and the ACP_PRESS PCM PID similar?
Yes
GO to F12.
No
INSTALL a new A/C pressure transducer. TEST the system for normal operation.
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F7 CHECK THE ACCS PCM INPUT
- Ignition OFF.
- Disconnect: PCM C175b.
- Ignition ON.
- Measure the voltage between PCM C175b-15, circuit 420 (DB/YE), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to F20.
No
GO to F8.
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F8 CHECK THE A/C CYCLING SWITCH VOLTAGE
- Ignition OFF.
- Disconnect: A/C Cycling Switch C130.
- Ignition ON.
- Measure the voltage between ground and A/C cycling switch C130-1, circuit 298 (VT/OG), harness side.
- Is the voltage greater than 10 volts?
Yes
GO to F9.
No
VERIFY SJB fuse 14 (5A) is OK. If OK, REPAIR circuit 298 (VT/OG) for an open. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. TEST the system for normal operation.
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F9 CHECK CIRCUIT 420 (DB/YE)/198 (DG/OG) FOR AN OPEN
- Ignition OFF.
- Disconnect: PCM C175b (4.0L only).
- Disconnect: Dual-Function Pressure Switch C1078 (4.6L and 5.4L only).
- NOTE: 4.0L only.
- Measure the resistance between A/C cycling switch C130-4, circuit 198 (DG/OG), harness side and PCM C175b-15, circuit 420 (DB/YE), harness side.
- NOTE: 4.6L and 5.4L only.
- Measure the resistance between A/C cycling switch C130-4, circuit 198 (DG/OG), harness side and dual-function pressure switch C1078-1, circuit 198 (DG/OG), harness side.
- Is the resistance less than 5 ohms?
Yes
For 4.0L, INSTALL a new A/C cycling switch. TEST the system for normal operation.
For 4.6L and 5.4L, GO to F10.
No
REPAIR circuit 420 (DB/YE)/198 (DG/OG) for an open. TEST the system for normal operation.
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F10 CHECK VOLTAGE TO THE DUAL-FUNCTION PRESSURE SWITCH
- Ignition OFF.
- Connect: A/C Cycling Switch C130.
- Ignition ON.
- Measure the voltage between dual-function pressure switch C1078-1, circuit 198 (DG/OG), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to F11.
No
INSTALL a new A/C cycling switch. TEST the system for normal operation.
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F11 CHECK CIRCUIT 420 (DB/YE) FOR AN OPEN
- Ignition OFF.
- Disconnect: PCM C175b.
- Measure the resistance between dual-function pressure switch C1078-4, circuit 420 (DB/YE), harness side and PCM C175b-15, circuit 420 (DB/YE), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new dual-function pressure switch. TEST the system for normal operation.
No
REPAIR circuit 420 (DB/YE) for an open. TEST the system for normal operation.
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F12 CHECK THE AIR CONDITIONING CLUTCH (WAC/ACCR) PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: WAC/ACCR PCM PID.
- With the engine running, select MAX A/C on the HVAC module.
- Does the WAC/ACCR PCM PID read ON?
Yes
GO to F13.
No
GO to F20.
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F13 CHECK THE GROUND AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Measure the resistance between A/C compressor clutch field coil C100-2, circuit 1205 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to F14.
No
REPAIR circuit 1205 (BK) for an open. TEST the system for normal operation.
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F14 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition ON.
- Select PANEL mode and press the A/C button on the HVAC module.
- With the engine running, measure the voltage between A/C compressor clutch field coil C100-1, circuit 883 (PK/LB), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to F15.
No
GO to F16.
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F15 CHECK THE A/C COMPRESSOR CLUTCH AIR GAP
- Measure the A/C compressor clutch air gap at 3 equally spaced locations between the clutch hub and the A/C compressor clutch pulley.
- Is the A/C compressor clutch air gap average greater than 0.65 mm (0.026 in)?
Yes
ADJUST the A/C compressor clutch gap. REFER to Air Conditioning (A/C) Clutch Air Gap Adjustment Adjustments. TEST the system for normal operation.
No
INSTALL a new A/C compressor clutch field coil. TEST the system for normal operation.
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F16 CHECK VOLTAGE TO RELAY SWITCH
NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use the test probe.
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between A/C control relay socket and ground.
- Is the voltage greater than 10 volts?
Yes
GO to F17.
No
VERIFY the Bussed Electrical Center (BEC) fuse 49 (15A) is OK. If OK, INSTALL a new BEC. If not OK, refer to the Wiring Diagrams to identify the possible causes of the circuit short. TEST the system for normal operation.
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F17 CHECK CIRCUIT 883 (PK/LB) FOR AN OPEN
NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use the test probe.
- Measure the resistance between A/C control relay socket, circuit 883 (PK/LB) and A/C compressor clutch field coil C100-1, circuit 883 (PK/LB), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new A/C control relay. TEST the system for normal operation.
No
REPAIR circuit 883 (PK/LB) for an open. TEST the system for normal operation.
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F18 CHECK THE SJB MODULE CONNECTION
- Clear the DTCs.
- Disconnect all the SJB connectors.
- Check for:
- corrosion.
- pushed-out pins.
- incorrectly seated connector.
- Connect and correctly seat all the SJB connectors.
- Operate the system.
- Does the concern return?
Yes
INSTALL a new SJB. 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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F19 CHECK THE MODULE CONNECTION
- Carry out the HVAC Module Cold Boot Process. HVAC Module Cold Boot Process
- Operate the system.
- Does the concern return?
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. TEST the system for normal operation.
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F20 CHECK THE PCM MODULE 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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