Pinpoint Test L: The Air Conditioning (A/C) is Inoperative

Climate Control System

Pinpoint Test L: The Air Conditioning (A/C) is Inoperative

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 Body Control Module (BCM), then from the BCM (Body Control Module) 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 (Instrument Cluster) DTCs first.

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 . 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.

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.

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.

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.

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.

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.

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. for component testing. If the relay tests OK, GO to L11.

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.

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. TEST the system for normal operation.

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 . TEST the system for normal operation.

No
INSTALL a new A/C compressor clutch field coil. TEST the system for normal operation.

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. [1][2]Diagrams By Number

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. [1][2]Diagrams By Number

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.

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.

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.

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. 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.

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.