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 Diagram Set 23 for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 24 for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 25 for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 26 for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, voltage is provided to the function selector switch through circuit CBP37 (WH). When A/C is requested, voltage is sent from the function selector switch to the A/C cycling switch through circuit CH434 (GY/YE). Voltage is sent from the A/C cycling switch to the dual-function pressure switch (diesel engine) or the A/C high pressure switch (gasoline engine) through circuit CH423 (YE). Voltage is sent from the dual-function pressure switch (diesel engine) or the A/C high pressure switch (gasoline engine) to the PCM through circuit CH419 (BU).
The PCM provides a ground for the A/C clutch relay coil through circuit CH302 (WH/BN). The A/C clutch relay coil receives ignition voltage through circuit CBB77 (WH). Battery voltage for the A/C clutch relay switch is provided through circuit SBB29 (GY/RD). When the relay is energized, voltage is supplied to the A/C clutch field coil through circuit (gasoline engine) CH401 (WH/VT) or (diesel engine) CH401 (WH/VT)/321 (GY/WH). Ground is supplied for the A/C clutch through circuit (gasoline engine) GD123 (BK/GY) or (diesel engine) 57 (BK).
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- PCM
- Function selector switch
- A/C cycling switch
- A/C high pressure switch
- A/C compressor clutch field coil
- A/C control relay
- A/C clutch air gap
PINPOINT TEST E: THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTICE: It is important to install relays in their correct position in the Battery Junction Box (BJB). Installing a relay incorrectly may cause wiring shorts or damage to modules. While carrying out diagnostics on BJB relays, have only one BJB relay removed at a time. Failure to follow these instructions may result in damage to the vehicle circuitry or to control modules.
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: Diesel Engines: Dual Function Pressure Switch C1062.
- Disconnect: Gasoline Engines: A/C High Pressure Switch C1078.
- Ignition ON.
For diesel engines
- For diesel engines: Measure the voltage between dual function pressure switch C1062-1, circuit CH423 (YE) and ground.
For gasoline engines
- For gasoline engines: 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 CIRCUIT CH434 (GY/YE) FOR AN OPEN
- Ignition OFF.
- Measure the resistance between function selector switch C194a-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. 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 DUAL FUNCTION PRESSURE OR A/C HIGH PRESSURE SWITCH
- Ignition OFF.
For diesel engines
- For diesel engines: Connect a fused jumper lead between dual function pressure switch C1062-1, circuit CH423 (YE) and C1062-4, circuit CH419 (BU).
For gasoline engines
- For gasoline engines: 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 CIRCUIT CH419 (BU) OR CH421 (GY) FOR AN OPEN
- Ignition OFF.
- Remove the fused jumper lead from dual function pressure switch or high pressure switch connector.
- Disconnect: For diesel engines, PCM C1381b.
- Disconnect: For 4.6L & 5.4L gasoline engines, PCM C175b.
- Disconnect: For 6.8L gasoline engines, PCM C1551e.
For diesel engines
- For diesel engines: Measure the resistance between dual function pressure switch C1062-4, circuit CH419 (BU) and PCM C1381b-8, circuit CH419 (BU).
For 4.6L & 5.4L gasoline engines
- For 4.6L & 5.4L gasoline 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 gasoline engines
- For 6.8L gasoline 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 CH419 (BU) or 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:
- For diesel engines, A/C compressor clutch field coil C100-1, circuit CH321 (GY/WH), harness side.
- For gasoline engines, A/C compressor clutch field coil C100-1, circuit CH401 (WH/VT), 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:
- For diesel engines, A/C compressor clutch field coil C100-2, circuit 57 (BK), harness side.
- For gasoline engines, 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 CIRCUIT SBB29 (GY/RD) FOR AN OPEN
- Ignition OFF.
- Disconnect: A/C Control Relay.
- Measure the voltage between A/C control 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 CIRCUIT CH401 (WH/VT) FOR AN OPEN
- Measure the resistance between:
- For diesel engines, A/C control relay socket, circuit CH401 (WH/VT) and A/C compressor clutch field coil C100-1, circuit CH321 (GY/WH), harness side.
- For gasoline engines, A/C control relay socket, circuit CH401 (WH/VT) and A/C compressor clutch field coil C100-1, circuit CH401 (WH/VT), 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 CH401 (WH/VT) 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. TEST the system for normal operation.
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E15 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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