A/C System Circuits Check: Troubleshooting

WARNING: Keep hands, tools, and clothing away from A/C condenser fan to help prevent personal injury. This fan is electric and can come on whether or not the engine is running. The fan can start automatically in response to the ECT sensor with the ignition switch in the "ON" position.

NOTE:

Before performed troubleshooting, be sure to read the Precautions of ECM Circuit Inspection.
When measuring circuit voltage, resistance and/or pulse signal at ECM connector, connect the special tool to ECM and/or the ECM connectors referring to INSPECTION OF ECM AND ITS CIRCUITS .
When A/C evaporator outlet air temp. is below 0 °C (32 °F), A/C remains OFF. This condition is not abnormal.

DTC TROUBLESHOOTING CHART

Step	Action	YES	NO
1	Check DTC in ECM (Reception data check from BCM) Connect scan tool to DLC with ignition switch turned OFF. Turn ON ignition switch. Check DTC for reception data from BCM. Is there DTC U0140?	Go to applicable DTC diagnostic flow chart.	Go to Step 2.
2	DTC check of HVAC control module Check HVAC control module for DTC. Is there DTC(s)?	Go to applicable DTC diagnostic flow chart.	Go to Step 3.
3	A/C switch signal circuit check Start engine and select "DATA LIST" mode on scan tool. Check A/C switch signal under following conditions respectively. A/C switch signal Engine running, A/C switch OFF: OFF Engine running, A/C switch ON and blower speed selector turned 1st position or more: ON Is check result satisfactory?	Go to Step 4.	Check HVAC control module and its circuit.
4	DTC check of ECT sensor circuit Check ECM for DTC of ECT sensor circuit. Is there DTC P0116, DTC P0117 or DTC P0118?	Go to applicable DTC diagnostic flow chart.	Go to Step 5.
5	Radiator cooling fan control system check Is radiator cooling fan started when A/C and blower speed selector switch are turned ON with engine running?	Go to Step 11.	Go to Step 6.
6	Radiator cooling fan control circuit check Check DTC with scan tool. Are DTC P0480, DTC P0481 and/or DTC P0482 detected?	Go to applicable DTC diagnostic flow chart.	Go to Step 7.
7	Evaporator temperature sensor check Check evaporator temperature sensor referring to A/C EVAPORATOR TEMPERATURE SENSOR INSPECTION . Is resistance within specification?	Go to Step 8.	Faulty evaporator temperature sensor.
8	DTC check of A/C refrigerant pressure sensor circuit Connect scan tool to DLC with ignition switch turned OFF. Turn ON ignition switch. Check ECM for DTC of A/C refrigerant pressure sensor circuit. Is there DTC P0532 or DTC P0533?	Go to applicable DTC diagnostic flow chart.	Go to Step 9.
9	A/C refrigerant pressure sensor voltage check Check A/C refrigerant pressure sensor voltage referring to INSPECTION OF ECM AND ITS CIRCUITS . Is voltage within specified value?	Go to Step 10.	Check amount of refrigerant. If OK, replace A/C refrigerant pressure sensor.
10	Radiator cooling fan check Check radiator cooling fan referring to RADIATOR COOLING FAN MOTOR ON-VEHICLE INSPECTION . Is check result satisfactory?	Radiator cooling fan drive circuit malfunction.	Replace radiator cooling fan motor.
11	A/C compressor control system check Is A/C compressor started when A/C and blower speed selector switch are turned ON with engine running?	A/C system is in good condition.	Go to Step 12.
12	A/C compressor relay circuit check Measure voltage between "E23-37" wire terminal of ECM connector and vehicle body ground under following conditions respectively. Voltage between "E23-37" terminal of ECM connector and ground While engine running and A/C switch turned OFF: 10 - 14 V While engine running, A/C and blower speed selector switch turned ON: 0 - 1 V Is check result satisfactory?	Go to Step 13.	Go to Step 14.
13	A/C compressor relay check Check A/C compressor relay referring to A/C COMPRESSOR RELAY INSPECTION . Is it in good condition?	A/C compressor drive circuit malfunction.	Replace A/C compressor relay.
14	A/C compressor relay circuit check Remove A/C compressor relay with ignition switch turned OFF. Turn ON ignition switch, measure voltage between "YEL/GRN" wire terminal of A/C compressor relay connector and vehicle body ground. Is voltage 10-14 V?	Go to Step 15.	"YEL/GRN" wire is open circuit.
15	A/C compressor relay check Check A/C compressor relay referring to A/C COMPRESSOR RELAY INSPECTION . Is it in good condition?	"PNK" wire is open circuit. If OK, substitute a known-good ECM and recheck.	Replace A/C compressor relay.