No. 18 Cooling System Concerns-Runs Cold

18	COOLING SYSTEM CONCERNS-RUNS COLD
DESCRIPTION	The engine takes excessive time to reach the normal operating temperature.
POSSIBLE CAUSE	Thermostat malfunction Eccentric shaft bypass malfunction (stuck open) 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	Inspect the cooling fan control system operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION ). Does the cooling fan control system work 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 operation. (See THERMOSTAT REMOVAL/INSTALLATION ). (See THERMOSTAT INSPECTION ). Is the thermostat normal?	Yes	Install the thermostat. (See THERMOSTAT REMOVAL/INSTALLATION ). Go to the next step.
4		No	(See THERMOSTAT REMOVAL/INSTALLATION ).
5	Access the ECT PID. (See ON-BOARD DIAGNOSTIC TEST ). Inspect the readings on both the ECT PID and the water temperature gauge on the instrument cluster. Is the ECT PID indication the same as the water temperature gauge readings?	Yes	Inspect the eccentric shaft bypass valve.
5		No	If the water temperature gauge is in the normal range but the ECT PID is not the same as the water temperature gauge reading, inspect the ECT sensor. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION ). If the water temperature gauge on the instrument cluster indicates the cold range but the ECT PID is normal, inspect the water temperature gauge. (See INSTRUMENT CLUSTER INSPECTION ).
6	Verify test results. If normal, return to the diagnostic index to service any additional symptoms. 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.