Diagnostic Procedure
WARNING: This page is about a different car, the 2002 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.
- Remove cooling fan relays No. 2 and 3. See Fig 1. Start engine. Turn A/C on. Move temperature lever to full cold position. Turn blower motor on. Run engine a few minutes with A/C running. If cooling fan is operating at low speed, go to next step. If cooling fan does not operate at low speed, perform PROCEDURE "A" .
- Turn ignition off. Install cooling fan relays No. 2 and 3. Remove cooling fan relay No. 1. Turn A/C and blower off. Disconnect ECT sensor harness connector. See Figure. Connect a 150 ohm resistor between ECT sensor harness connector terminals. Start engine. Cooling fan should operate at a higher speed that in previous step. If cooling fan operates as specified, go to next step. If cooling fan does not operate as specified, perform PROCEDURE "B" .
- Pressure test cooling system and radiator cap. Remove thermostat. Inspect thermostat valve seating condition at room temperature. Thermostat valve should seat tightly. Check thermostat valve opening temperature and lift. Thermostat valve should lift more than .35 in (9.0 mm) at 194°F (90°C). If a problem is found, repair as necessary. If no problems are found, go to next step.
- Remove ECT sensor and place in heated water. Measure resistance between ECT sensor terminals, with water at specified temperatures. See ECT SENSOR RESISTANCE table. If resistance is not as specified, replace ECT sensor and retest system. If resistance is as specified, check for other possible cause of engine overheating and repair as necessary. Test is complete.
ECT SENSOR RESISTANCE
| Temperature - °F (°C) | (1) Ohms | ||
|---|---|---|---|
| 68 (20) | 2100-2900 | ||
| 122 (50) | 680-1000 | ||
| 194 (90) | 236-260 | ||
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