check the wiring or the connector. if the 2 wires are shorted together. then you will get a high volts on the sensor. and then you can read across the sensor wen the motor is cold it should have High Resistance. wen the motor heats up the res should get Lower.
What does that mean?
The
engine coolant temperature (ECT) sensor is a thermistor screwed into a coolant passage in the cylinder head. Sensor resistance is high when coolant temperature is low and resistance drops when coolant temperature increases. The powertrain control module (PCM) provides a 5 volt reference and a ground to the sensor. The PCM monitors voltage drop to determine coolant temperature. If the ECT reads less than freezing temp. when engine has been running for more than a few minutes, the PCM determines a circuit fault and sets this code. Or if the PCM determines the sensor resistance is out of specs, this code is set.
Potential Symptoms
Symptoms of a P0118 could include:
- Very poor fueleconomy
- A no start condition
- Vehicle may start, but run very poorly, blowing black smoke, running very rough and misfiring
- Illumination of MIL
Causes
A code P0118 may mean that one or more of the following has happened:
- A bad connection at the sensor
- An open in the ground circuit between the ECT sensor and the PCM
- A short in the voltage feed between the sensor and the PCM
- A bad PCM (less likely)
- A bad temperature sensor (shorted internally)