DTC P0115 OR P0125 - ENGINE COOLANT TEMPERATURE (ECT) SENSOR Nissan 240SX S14

1. Check Power Supply Turn ignition off. Disconnect ECT sensor harness connector. (Scheme 17) Turn ignition on. Measure voltage between ECT sensor harness connector terminal "2" (Blue/Orange wire) and ground. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, repair harness or connectors as necessary.
2. Check Ground Circuit Turn ignition off. Check for continuity between terminal "1" (Black wire) and engine ground. If continuity is present, go to next step. If continuity is not present, check harness continuity between ECT sensor and ECM, or between ECT sensor and A/T control unit. Repair harness or connectors as necessary.
3. 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.

Scheme 17