Diagnostic Procedure

NO. 18 COOLING SYSTEM CONCERNS-RUNS COLD DIAGNOSTIC PROCEDURE

STEP	INSPECTION	RESULTS	ACTION
1	DETERMINE IF MALFUNCTION CAUSE IS HVAC SYSTEM OR ENGINE Is the customer complaint "Lack of passenger compartment heat" only?	Yes	Inspect the A/C and heater system. Repair or replace the malfunctioning part according to the inspection results.
1		No	Go to the next step.
2	VERIFY IDLE SPEED Does the engine speed continue at fast idle?	Yes	Go to the symptom troubleshooting "NO. 9 FAST IDLE/RUNS ON". (See NO. 9 FAST IDLE/RUNS ON .)
2		No	Go to the next step.
3	INSPECT COOLING FAN CONTROL SYSTEM OPERATION Perform the Cooling Fan Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION .) Does the cooling fan control system operate properly?	Yes	Go to the next step.
3		No	Repair or replace the malfunctioning part according to the inspection results.
4	INSPECT THERMOSTAT Cool down the engine. Remove the thermostat. (See THERMOSTAT REMOVAL/INSTALLATION .) Inspect the thermostat operation. (See THERMOSTAT INSPECTION .) Is there any malfunction?	Yes	Replace the thermostat. (See THERMOSTAT REMOVAL/INSTALLATION .)
4		No	Reinstall the thermostat, then go to the next step. (See THERMOSTAT REMOVAL/INSTALLATION .)
5	INSPECT ECT SENSOR SIGNAL Access the ECT PID using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST .) Compare the ECT PID and low engine coolant temperature indicator light and high engine coolant temperature warning light operation. Is the ECT PID value same as indicator/warning light readings?	Yes	Go to the next step.
5		No	Inspect the ECT sensor. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION .) If there is any malfunction: Replace the ECT sensor. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL/INSTALLATION .) If there is no malfunction: Replace the instrument cluster. (See INSTRUMENT CLUSTER REMOVAL/INSTALLATION .)
6	Verify test results. If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX .) If the malfunction remains, inspect the related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis. If the vehicle is repaired, troubleshooting is completed. If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if a later calibration is available. Retest.