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 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 A/C is requested, in the Dual Automatic Temperature Control (DATC) system, a message is sent over the Medium Speed Controller Area Network (MS-CAN) bus from the HVAC module - DATC to the Instrument Cluster (IC), then from the IC through the High Speed Controller Area Network (HS-CAN) bus to the PCM.
Under normal operation, when A/C is requested, in the Electronic Manual Temperature Control (EMTC) system, voltage is sent to the IC from the HVAC module - EMTC, then a message is sent from the IC through the HS-CAN bus to the PCM.
Voltage is provided to the A/C clutch relay switch contacts. When the PCM energizes the relay, voltage is supplied to the A/C compressor clutch field coil. The A/C compressor clutch field coil is grounded.
When an A/C request is received by the PCM, the A/C compressor clutch will only be engaged through the A/C clutch relay if all of the following conditions are met:
- 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).
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 HVAC to turn off the A/C compressor when the evaporator temperatures are cold enough to freeze the condensation. This prevents ice blockage of airflow over the evaporator core.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- PCM
- HVAC module - DATC
- HVAC module - EMTC
- A/C evaporator temperature sensor
- A/C pressure transducer
- A/C compressor
- A/C control relay
- Battery Junction Box (BJB)
PINPOINT TEST L: THE AIR CONDITIONING (A/C) IS INOPERATIVE
NOTE: Before carrying out the following test, diagnose any HVAC, PCM or IC 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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L1 CHECK THE A/C PRESSURE SENSOR (ACP_PSI) PCM PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: ACP_PSI PCM PID.
- With the manifold gauge set connected, compare the pressure readings of the manifold gauge set and the ACP_PSI PID.
- Are the pressure values of the manifold gauge set and the ACP_PSI PID similar?
Yes
GO to L2.
No
INSTALL a new A/C pressure transducer. TEST the system for normal operation.
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L2 CHECK THE POST EVAPORATOR TEMPERATURE SENSOR INPUT (PEVAP_TMP) HVAC PID
- Allow the vehicle exterior and interior to stabilize to ambient temperature.
- Enter the following diagnostic mode on the scan tool: PEVAP_TMP HVAC PID.
- Does the PEVAP_TMP HVAC PID read similar to the ambient temperature?
Yes
For DATC systems, GO to L3.
For EMTC systems, GO to L4.
No
CARRY OUT the Evaporator Temperature Sensor component test Evaporator Temperature Sensor. If the sensor tests OK, GO to L13. If the sensor does not test OK, INSTALL a new heater core and evaporator core housing. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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L3 CHECK THE AIR CONDITIONING SWITCH STATUS (CC_AC) HVAC PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: CC_AC HVAC PID.
- Press the PANEL and A/C manual override buttons on the HVAC module - DATC.
- Does the CC_AC HVAC PID read ON?
Yes
GO to L5.
No
GO to L13.
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L4 CHECK THE HVAC MODULE - EMTC A/C SIGNAL WITH THE A/C ON
NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tools table at the beginning. To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.
- Ignition OFF.
- Disconnect: IC C220.
- Ignition ON.
- Select PANEL mode and press the A/C button on the HVAC module - EMTC.
- Connect a 12-volt test light between IC C220-23, circuit CH434 (GY/YE), harness side and IC C220-19, circuit SBP26 (YE/RD), harness side.
- Does the test light illuminate?
Yes
GO to L5.
No
GO to L7.
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L5 CHECK THE AIR CONDITIONING COMPRESSOR CYCLING SWITCH (ACCS) PCM PID WITH THE A/C ON
- Ignition OFF.
- NOTE: EMTC systems only.
- Connect: EMTC Systems Only, IC C220.
- Ignition ON.
- NOTE: EMTC systems only.
- Enter the following diagnostic mode on the scan tool: ACCS PCM PID.
- With the engine running, press the PANEL and A/C manual override buttons on the HVAC module - DATC or select MAX A/C on the HVAC module - EMTC.
- Does the ACCS PCM PID read ON?
Yes
GO to L6.
No
GO to L14.
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L6 CHECK THE AIR CONDITIONING CLUTCH (WAC/ACCR) PCM PID WITH THE A/C ON
- Enter the following diagnostic mode on the scan tool: WAC/ACCR PCM PID.
- Does the WAC/ACCR PCM PID read ON?
Yes
GO to L9.
No
GO to L14.
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L7 CHECK CIRCUIT CH434 (GY/YE) FOR AN OPEN
- Ignition OFF.
- Disconnect: HVAC Module - EMTC C2357A.
- Measure the resistance between HVAC module - EMTC C2357A-2, circuit CH434 (GY/YE), harness side and IC C220-23, circuit CH434 (GY/YE), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to L8.
No
REPAIR circuit CH434 (GY/YE) for an open. TEST the system for normal operation.
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L8 CHECK CIRCUIT CH434 (GY/YE) FOR A SHORT TO VOLTAGE
- Ignition ON.
- Measure the voltage between HVAC module - EMTC C2357A-2, circuit CH434 (GY/YE), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit CH434 (GY/YE) for a short to voltage. TEST the system for normal operation.
No
GO to L14.
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L9 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, press the PANEL and A/C manual override buttons on the HVAC module - DATC or select MAX A/C on the HVAC module - EMTC.
- 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 L10.
No
CARRY OUT the A/C Control Relay component test.
If the relay tests OK, GO to L11.
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L10 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 GD120 (BK/GN), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new A/C compressor. TEST the system for normal operation.
No
REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.
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L11 CHECK THE RELAY SWITCH FOR VOLTAGE
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between A/C clutch relay socket and ground.
- Is the voltage greater than 10 volts?
Yes
GO to L12.
No
VERIFY BJB fuse 35 (10A) is OK. If OK, INSTALL a new BJB. TEST the system for normal operation.
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L12 CHECK CIRCUIT CH401 (VT/WH) FOR AN OPEN
- Ignition OFF.
- 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
GO to L14.
No
REPAIR circuit CH401 (VT/WH) for an open. TEST the system for normal operation.
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L13 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.
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L14 CHECK THE PCM CONNECTION
- Disconnect all the PCM connectors.
- Inspect the 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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