Pinpoint Test E: The Air Conditioning (A/C) is Inoperative
Climate Control System
Pinpoint Tests
Pinpoint Test E: 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
Refer to Wiring Diagrams for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, voltage is provided to the function selector switch. When A/C is requested, voltage is sent from the function selector switch to the A/C cycling switch. Voltage is sent from the A/C cycling switch through the A/C high pressure switch to the PCM.
Voltage is provided to the A/C clutch relay coil and switch contacts. When A/C is requested and A/C line pressures allow, a ground is provided to the A/C clutch relay coil from the PCM, energizing the A/C clutch relay. When the PCM energizes the relay, voltage is supplied to the A/C clutch from the relay. Ground is supplied for the A/C clutch.
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- Low refrigerant system charge
- PCM
- Function selector switch
- A/C cycling switch
- A/C high pressure switch
- A/C compressor clutch field coil
- A/C clutch relay
- A/C compressor clutch air gap
PINPOINT TEST E: THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTE: Before carrying out the following test, diagnose any PCM DTCs.
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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E1 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQ) PCM PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: AC_REQ PCM PID.
- With the engine running, place the function selector switch in the MAX A/C position.
- Does the AC_REQ PCM PID read YES?
Yes
GO to E2.
No
GO to E3.
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E2 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 YES?
Yes
GO to E10.
No
GO to E15.
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E3 CHECK THE A/C HIGH PRESSURE SWITCH VOLTAGE
- Ignition OFF.
- Disconnect: A/C High Pressure Switch C1078.
- Ignition ON.
- Measure the voltage between A/C high pressure switch C1078-3, circuit CH423 (YE) and ground.
- Is the voltage greater than 10 volts?
Yes
GO to E8.
No
GO to E4.
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E4 CHECK THE A/C CYCLING SWITCH VOLTAGE
- Ignition OFF.
- Disconnect: A/C Cycling Switch C130.
- Ignition ON.
- Measure the voltage between A/C cycling switch C130-1, circuit CH434 (GY/YE), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to E5.
No
GO to E6.
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E5 CHECK THE A/C CYCLING SWITCH
- Ignition OFF.
- Measure the resistance between the A/C cycling switch terminals.
- Is the resistance less than 21 ohms?
Yes
REPAIR circuit CH423 (YE) for an open. TEST the system for normal operation.
No
INSTALL a new A/C cycling switch. TEST the system for normal operation.
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E6 CHECK THE VOLTAGE AT THE FUNCTION SELECTOR SWITCH
- Ignition OFF.
- Disconnect: Function Selector Switch C294A.
- Ignition ON.
- Measure the voltage between function selector switch C294A-1, circuit CBP37 (WH), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to E7.
No
VERIFY the Smart Junction Box (SJB) fuse 37 (10A) is OK. If OK, REPAIR circuit CBP37 (WH) for an open. TEST the system for normal operation.
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E7 CHECK THE FUNCTION SELECTOR SWITCH TO A/C CYCLING SWITCH CIRCUIT FOR AN OPEN
- Ignition OFF.
- Measure the resistance between function selector switch C294A-2, circuit CH434 (GY/YE), harness side and A/C cycling switch C130-1, circuit CH434 (GY/YE), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new function selector switch. REFER to Climate Control Function Selector Switch. TEST the system for normal operation.
No
REPAIR circuit CH434 (GY/YE) for an open. TEST the system for normal operation.
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E8 CHECK THE A/C HIGH PRESSURE SWITCH
- Ignition OFF.
- Connect a fused jumper lead between A/C high pressure switch C1078-3, circuit CH423 (YE) and C1078-1, circuit CH421 (GY).
- Ignition ON.
- With the engine running, does the A/C compressor operate?
Yes
INSTALL a new A/C high pressure switch. TEST the system for normal operation.
No
GO to E9.
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E9 CHECK THE A/C HIGH PRESSURE SWITCH TO PCM CIRCUIT FOR AN OPEN
- Ignition OFF.
- Remove the fused jumper lead from the A/C high pressure switch connector.
- Disconnect: For 4.6L and 5.4L engines, PCM C175B.
- Disconnect: For 6.8L engines, PCM C1551E.
For 4.6L and 5.4L engines
- For 4.6L and 5.4L engines: Measure the resistance between A/C high pressure switch C1078-1, circuit CH421 (GY) and PCM C175B-57, circuit CH421 (GY).
For 6.8L engines
- For 6.8L engines: Measure the resistance between A/C high pressure switch C1078-1, circuit CH421 (GY) and PCM C1551E-4, circuit CH421 (GY).
- Is the resistance less than 5 ohms?
Yes
GO to E15.
No
REPAIR circuit CH421 (GY) for an open. TEST the system for normal operation.
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E10 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Ignition ON.
- With the engine running, measure the voltage between ground and A/C compressor clutch field coil C100-1, circuit CH401 (VT/WH), harness side.
- Is the voltage greater than 10 volts?
Yes
GO to E11.
No
GO to E12.
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E11 CHECK THE GROUND AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Measure the resistance between ground and A/C compressor clutch field coil C100-2, circuit GD123 (BK/GY), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to E14.
No
REPAIR circuit GD123 (BK/GY) for an open. TEST the system for normal operation.
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E12 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY SWITCH CONTACTS
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Measure the voltage between A/C clutch relay socket 3, circuit SBB29 (GY/RD) and ground.
- Is the voltage greater than 10 volts?
Yes
GO to E13.
No
VERIFY the Battery Junction Box (BJB) fuse 29 (10A) is OK. If OK, REPAIR circuit SBB29 (GY/RD) for an open. TEST the system for normal operation. If the fuse is open, INSTALL a new 10A fuse. TEST the system for normal operation. If fuse opens again, REPAIR the circuit for a short.
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E13 CHECK THE A/C COMPRESSOR CLUTCH FIELD COIL VOLTAGE CIRCUIT FOR AN OPEN
- Measure the resistance between A/C clutch relay socket, circuit CH401 (VT/WH) and A/C compressor clutch field coil C100-1, circuit CH401 (VT/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new A/C clutch relay. TEST the system for normal operation.
No
REPAIR circuit CH401 (VT/WH) for an open. TEST the system for normal operation.
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E14 CHECK THE A/C COMPRESSOR CLUTCH AIR GAP
- Measure the A/C compressor clutch air gap at 3 equally spaced locations between the clutch disc and hub assembly 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 air 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. REFER to Climate Control Service and Repair. TEST the system for normal operation.
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E15 CHECK THE PCM CONNECTION
- Disconnect all the PCM connectors.
- Inspect the HVAC 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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