No. 18 Cooling System Concerns-Runs Cold

18	COOLING SYSTEM CONCERNS-RUNS COLD
DESCRIPTION	The engine takes excessive time to reach normal operating temperature.
POSSIBLE CAUSE	A/C and heater system malfunction Thermostat malfunction Cooling fan system malfunction

DIAGNOSTIC PROCEDURE

STEP	INSPECTION	RESULTS	ACTION
1	Is the customer complaint "Lack of passenger compartment heat" only?	Yes	Inspect the A/C and heater system.
1		No	Go to the next step.
2	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	Does the engine speed continue at fast idle?	No	Go to the next step.
3	Perform the Cooling Fan Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION ). Does the cooling fan control system function properly?	Yes	Go to the next step.
3		No	Repair or replace the malfunctioning part according to the inspection results.
4	Cool down the engine. Remove the thermostat and inspect the operation. (See THERMOSTAT REMOVAL/INSTALLATION ). (See THERMOSTAT INSPECTION ). Is the thermostat normal?	Yes	Access the ECT PID. Inspect for both ECT PID and temperature gauge on instrument cluster readings. If the temperature gauge on the instrument cluster indicates normal range but the ECT PID is not the same as temperature gauge reading, inspect the ECT sensor. If the temperature gauge on the instrument cluster indicates cold range but the ECT PID is normal, inspect the instrument cluster.
4		No	Replace the thermostat. (See THERMOSTAT REMOVAL/INSTALLATION ).
5	Verify test results. If normal, return to diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX ). If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis. If vehicle is repaired, troubleshooting completed. If vehicle is not repaired or additional diagnostic information is not available, replace the PCM. (See PCM REMOVAL/INSTALLATION ).