Pinpoint Test L: The Air Conditioning (A/C) is Inoperative
Climate Control System
Pinpoint Tests
Pinpoint Test L: The Air Conditioning (A/C) is Inoperative
Refer to Wiring Diagram Set 25, Electronic Engine Controls - 6.8L for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 26, Electronic Engine Controls - 6.2L for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 27, Electronic Engine Controls - 6.7L Diesel for schematic and connector information. Diagrams By Number
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, when the A/C is requested, an A/C request message is sent from the HVAC module over the Medium Speed Controller Area Network (MS-CAN) bus to the Instrument Panel Cluster (IPC), then from the IC through the High Speed Controller Area Network (HS-CAN) bus 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.
The evaporator temperature sensor is used for A/C compressor cycling. An accurate evaporator temperature is critical for compressor engagement. The temperature measurement is used by the PCM to turn the A/C compressor off before the evaporator temperatures are cold enough to freeze the condensation on the evaporator core.
When an A/C request is received by the PCM, the A/C compressor clutch only engages through the A/C clutch relay if all of the following conditions are met:
- DTC P145B (A/C Demand Not Activated During Self Test) - The module senses no change from the pressure transducer when A/C is commanded on during the self-test.
- 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 temperature below 2°C (36°F).
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- A/C system discharged/low charge
- PCM
- HVAC module
- Evaporator temperature sensor
- A/C pressure transducer
- A/C compressor clutch field coil
- A/C clutch relay
- A/C compressor clutch air gap
PINPOINT TEST L: THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTE: Before carrying out the following test, diagnose any HVAC, PCM or IC DTCs first.
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L1 CHECK THE A/C SYSTEM PRESSURE
- Ignition OFF.
- With the R-134a manifold gauge set connected, check the A/C system pressure.
- Is the A/C system pressure above 290 kPa (42 psi) ?
Yes
GO to L2.
No
CHECK the A/C system for leaks. REFER to Fluorescent Dye Leak Detection Fluorescent Dye Leak Detection or Electronic Leak Detection Electronic Leak Detection. RECHARGE the A/C system. REFER to Air Conditioning (A/C) System Recovery, Evacuation and Charging Air Conditioning (A/C) System Recovery, Evacuation and Charging. TEST the system for normal operation.
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L2 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 PCM PID.
- Are the pressure values of the manifold gauge set and the ACP_PRESS PCM PID similar?
Yes
GO to L3.
No
INSTALL a new A/C pressure transducer. TEST the system for normal operation.
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L3 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC PID
- Allow the vehicle exterior and interior to stabilize to the outside 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
GO to L4.
No
INSTALL a new evaporator temperature sensor. TEST the system for normal operation.
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L4 CHECK THE A/C SWITCH (CC_SW_AC) HVAC PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: CC_SW_AC HVAC PID.
- Select PANEL press the A/C button (indicator on) on the HVAC controls.
- Does the CC_SW_AC HVAC PID read ON?
Yes
GO to L5.
No
GO to L16.
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L5 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQ) PCM PID WITH THE A/C ON
- Start the engine.
- Enter the following diagnostic mode on the scan tool: AC_REQ PCM PID.
- Select PANEL press the A/C button (indicator on) on the HVAC controls.
- Does the AC_REQ PCM PID read YES?
Yes
GO to L6.
No
GO to L16.
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L6 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.
- Select PANEL press the A/C button (indicator on) on the HVAC controls.
- Does the ACC_CMD PCM PID read ON?
Yes
GO to L7.
No
GO to L17.
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L7 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Start the engine.
- Select PANEL and A/C on the HVAC module.
- Measure the voltage between A/C compressor clutch field coil C100-1, circuit CH401 (VT/WH), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to L8.
No
CARRY OUT the A/C clutch relay component test.
If the relay tests OK, GO to L11.
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L8 CHECK THE GROUND AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Measure the resistance between A/C compressor clutch field coil C100-2, circuit GD124 (BK/VT) or GD122 (BK) (diesel), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to L9.
No
REPAIR circuit GD124 (BK/VT) or GD122 (BK) (diesel) for an open. TEST the system for normal operation.
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L9 CHECK THE A/C COMPRESSOR CLUTCH FIELD COIL
- Measure the resistance between the A/C compressor clutch field coil C100 terminals, component side.
- Is the resistance 2-5 ohms?
Yes
GO to L10.
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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L10 CHECK THE A/C COMPRESSOR CLUTCH FIELD COIL FOR A SHORT TO GROUND
- Measure the resistance between the A/C compressor clutch field coil C100 terminals, component side and ground.
- Is the resistance greater than 10,000 ohms?
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. REFER to Climate Control Service and Repair. TEST the system for normal operation.
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L11 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY SWITCH CONTACTS
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between A/C clutch relay socket, circuit SBB47 (WH/RD) and ground.
- Is the voltage greater than 10 volts?
Yes
GO to L12.
No
VERIFY Battery Junction Box (BJB) fuse 47 (10A) is OK. If OK, REPAIR circuit SBB47 (WH/RD) for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number
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L12 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY COIL
- Measure the voltage between A/C clutch relay socket, circuit CBB35 (YE/GY) and ground.
- Is the voltage greater than 10 volts?
Yes
GO to L13.
No
VERIFY Battery Junction Box (BJB) fuse 35 (10A) is OK. If OK, REPAIR circuit CBB35 (YE/GY) for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number
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L13 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 greater than 10,000 ohms?
Yes
GO to L14.
No
REPAIR circuit CH401 (VT/WH) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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L14 CHECK THE A/C CLUTCH RELAY COIL SWITCHED GROUND CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: PCM C175B (Gasoline).
- Disconnect: PCM C1232B (Diesel).
- Ignition ON.
For gasoline engines
- Measure the voltage between ground and PCM C175B-12, circuit CH302 (WH/BN), harness side.
For diesel engines
- Measure the voltage between ground and PCM C1232B-2, circuit CH302 (WH/BN), harness side.
- Is any voltage present?
Yes
REPAIR circuit CH302 (WH/BN) for a short to voltage. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
GO to L15.
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L15 CHECK THE A/C CLUTCH RELAY COIL SWITCHED GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
For gasoline engines
- Measure the resistance between A/C clutch relay socket, circuit CH302 (WH/BN) and PCM C175B-12, circuit CH302 (WH/BN), harness side.
For diesel engines
- Measure the resistance between A/C clutch relay socket, circuit CH302 (WH/BN) and PCM C1232B-2, circuit CH302 (WH/BN), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to L17.
No
REPAIR circuit CH302 (WH/BN) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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L16 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. REFER to Climate Control Heating Ventilation Air Conditioning (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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L17 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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