- Check Ground Circuit Turn ignition switch to OFF position. Disconnect ECT harness connector. Using an ohmmeter, check continuity between harness connector terminal No. 1 (Black wire) and engine ground. If no continuity exists, repair open in Black wire. If continuity exists, go to next step.
- Check Power Supply Turn ignition switch to ON position. Using a voltmeter, measure voltage between ECT sensor harness connector terminal No. 2 (Brown/Yellow wire) and ground. If voltage is not approximately 5 volts, repair fault in Brown/Yellow wire as required. If measured voltage is approximately 5 volts, go to next step.
- Check Component Ensure ECT sensor is not damaged or contaminated. Check ECM and ECT sensor harness connectors for damage, corrosion or pushed-out pins. Repair if necessary. If no problems are found, ensure ignition is off. Measure resistance between ECT sensor connector terminals as follows: With temperature at 68°F (20°C), resistance should be 2100-2900 ohms. With temperature at 122°F (50°C), resistance should be 680-1000 ohms. With temperature at 194°F (90°C), resistance should be 236-260 ohms.
If resistance is not as specified, replace ECT sensor.