NO.18 COOLING SYSTEM CONCERNS-RUNS COLD [MZI-3.7]

id0103d2802400

18

COOLING SYSTEM CONCERNS—RUNS COLD

DESCRIPTION

•  Engine takes excessive time to reach normal operating temperature.

POSSIBLE CAUSE

•  A/C and heater system malfunction

•  Cooling fan system malfunction

•  Thermostat malfunction

•  Improper water temperature gauge operation

―  CHT sensor malfunction

―  Instrument cluster malfunction

18	COOLING SYSTEM CONCERNS—RUNS COLD
DESCRIPTION	• Engine takes excessive time to reach normal operating temperature.
POSSIBLE CAUSE	• A/C and heater system malfunction • Cooling fan system malfunction • Thermostat malfunction • Improper water temperature gauge operation ― CHT sensor malfunction ― Instrument cluster malfunction

Diagnostic procedure

STEP	INSPECTION	RESULTS	ACTION
1	Is 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	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 [MZI-3.7].)
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 [MZI-3.7].) 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 [MZI-3.7].) (See THERMOSTAT INSPECTION [MZI-3.7].) Is the thermostat normal?	Yes	Inspect the water temperature gauge. (See INSTRUMENT CLUSTER INSPECTION.) Repair or replace the malfunctioning part according to the inspection results. • If the water temperature gauge reading is normal, inspect the CHT sensor. (See CYLINDER HEAD TEMPERATURE (CHT) SENSOR INSPECTION [MZI-3.7].) • Repair or replace the malfunctioning part according to the inspection results.
4		No	Replace the thermostat. (See THERMOSTAT REMOVAL/INSTALLATION [MZI-3.7].)
5	• Verify test results. ― If normal, return to diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [MZI-3.7].) ― If malfunction remains, inspect related Service 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 [MZI-3.7].)