NO.18 COOLING SYSTEM CONCERNS-RUNS COLD [MZR 1.3, MZR 1.5]

id0103d7802400

18

COOLING SYSTEM CONCERNS—RUNS COLD

DESCRIPTION

•  The engine does not reach normal operating temperature.

POSSIBLE CAUSE

•  Cooling fan system malfunction

•  Thermostat malfunction

•  Improper indication of low engine coolant temperature indicator light and high engine coolant temperature warning light

―  ECT sensor malfunction

―  Instrument cluster malfunction

•  PCM malfunction

18	COOLING SYSTEM CONCERNS—RUNS COLD
DESCRIPTION	• The engine does not reach normal operating temperature.
POSSIBLE CAUSE	• Cooling fan system malfunction • Thermostat malfunction • Improper indication of low engine coolant temperature indicator light and high engine coolant temperature warning light ― ECT sensor malfunction ― Instrument cluster malfunction • PCM malfunction

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 [MZR 1.3, MZR 1.5].)
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 [MZR 1.3, MZR 1.5].) • 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 [MZR 1.3, MZR 1.5].) • Inspect the thermostat operation. (See THERMOSTAT INSPECTION [MZR 1.3, MZR 1.5].) • Is there any malfunction?	Yes	Replace the thermostat. (See THERMOSTAT REMOVAL/INSTALLATION [MZR 1.3, MZR 1.5].)
4		No	Reinstall the thermostat, then go to the next step. (See THERMOSTAT REMOVAL/INSTALLATION [MZR 1.3, MZR 1.5].)
5	INSPECT ECT SENSOR SIGNAL • Access the ECT PID using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZR 1.3, MZR 1.5].) • 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 [MZR 1.3, MZR 1.5].) • If there is any malfunction: ― Replace the ECT sensor. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL/INSTALLATION [MZR 1.3, MZR 1.5].) • 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 [MZR 1.3, MZR 1.5].) • If the malfunction remains, inspect the related Service Information and perform the repair or diagnosis. ― If the vehicle is repaired, troubleshooting is completed. ― If the vehicle is not repaired or additional diagnostic information is not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [MZR 1.3, MZR 1.5].)