Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.

NO.18 COOLING SYSTEM CONCERNS-RUNS COLD 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	Remove the thermostat and inspect operation. (See THERMOSTAT REMOVAL/INSTALLATION .) (See THERMOSTAT INSPECTION .) Is the thermostat normal?	Yes	Go to the next step.
3		No	Replace the thermostat.
4	Inspect the cooling fan control system operation. (See COOLING FAN CONTROL SYSTEM INSPECTION .) Does the cooling fan control system work properly?	Yes	Go to the next step.
4		No	Repair or replace the malfunctioning part.
5	Access the ECT PID. Inspect readings on both the ECT PID and the temperature gauge on the instrument cluster. Is the ECT PID indication the same as the temperature gauge readings?	Yes	Inspect the eccentric shaft bypass valve. (See ECCENTRIC SHAFT BYPASS VALVE .)
5		No	If the temperature gauge is in the normal range but the ECT PID is not the same as the temperature gauge reading, inspect the ECT sensor. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION .) If the temperature gauge on the instrument cluster indicates the cold range but the ECT PID is normal, inspect the temperature gauge and the sending unit. (See WATER TEMPERATURE GAUGE .)
6	Verify test results. If normal, return to the diagnostic index to service any additional symptoms. If the malfunction remains, inspect related the Service Bulletins and/or the On-line Repair Information and perform the repair or diagnosis.