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2008 - MX-5 - Engine

NO.18 COOLING SYSTEM CONCERNS-RUNS COLD [LF]



18

COOLING SYSTEM CONCERNS-RUNS COLD

DESCRIPTION

Engine takes excessive time to reach normal operating temperature.

POSSIBLE CAUSE

  • Thermostat malfunction

  • Cooling fan system malfunction


Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION

1

Is customer complaint "Lack of passenger compartment heat" only?

Yes

Inspect A/C and heater system.

No

Go to the next step.

2

Does the engine speed continue at fast idle?

Yes

Go to symptom troubleshooting "No.9 Fast idle/runs on".

(See NO.9 FAST IDLE/RUNS ON [LF].)

No

Go to the next step.

3

Remove the thermostat and inspect operation.

(See THERMOSTAT REMOVAL/INSTALLATION [LF].)

(See THERMOSTAT INSPECTION [LF].)

Is thermostat normal?

Yes

Go to the next step.

No

Replace the thermostat.

4

Inspect cooling fan control system operation.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [LF].)

Does the cooling fan control system function properly?

Yes

Access 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 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 ECT PID is normal, inspect the temperature gauge and heat gauge unit.

No

Repair or replace the malfunctioning part.

5

  • Verify test results.

    • If normal, return to diagnostic index to service any additional symptoms.

      (See SYMPTOM DIAGNOSTIC INDEX [LF].)

    • 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 PCM.

        (See PCM REMOVAL/INSTALLATION [LF].)




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