Hyundai Repair: 2001 Sonata Engine Coolant Temp Sensor, coolant temperature sensor, coolant temp

Question
QUESTION: Hi Sir,
My 2001 sonata gave me the error code P0118, which is engine coolant temp circuit input high. I would like to know the exact location of this sensor and I can try test and replace it(better with diagram).I am an electrician, should be able to do it if I know where is the sensor. Thanks a lot

Frank

ANSWER: The coolant temperature sensor is located in the coolant housing on the transmission end of the engine under the ignition coil.  

In my experience, most of the problems with this coolant temperature sensor are intermittent, so attempts to troubleshoot usually prove fruitless.  If you'd like, you can view the schematics for the vehicle in the ETM section at www.hmaservice.com.  You'll need to register for a free account, and the site requires Internet Explorer.

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QUESTION: Thank you for your answer and you are right. My check engine light is ON and then OFF and then ON. It is intermittent. So what's your suggestion for this problem and is it important to my car or I can just neglect it? Or just go to the dealer? Thank you for your help.

Frank

Answer
If it were my car and I didn't have a scan tool to read current temperature, I'd just replace the sensor knowing there was a large probability it was the culprit.  It's a rather simple repair.  Unscrew the old one and screw in the new one (topping off the coolant if necessary).

While the ECM is detecting the issue, it's likely to make conclusions about coolant temperature based on intake air temperature and how long the engine has been running.  You'll probably not notice any change in how the car runs, but you may suffer decreased fuel economy.