P0118 Coolant temp sensor code and impact

FinKJ

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Strangely search did not bear fruit with this one. As I have understood this is quite common problem and the sensor issue does have some major effect.

I have a 2002 2.4 KJ and it randomly loses the coolant temperature sensor. When it does, I can see the temp go all over the place and finally drop to zero. As for the Jeep the effect is that it starts consuming gas like it's 1960s, runs rough, check engine light is lit and fault code is p0118. It still starts cold, blows blue smoke for a while after start and is not very collaborative (practically will not start) on starting with warm engine.

The sensor was replaced by a Jeep specialist and car test driven. After the replacement it worked fine for a week. Then I took it to light off road activities and returned from there with engine acting up (check engine light, fault code p0118, few coughs while driving, momentarily loss of power and temp gauge dropping to zero). I let it rest for the night and in the morning everything was fine. reset the fault code and game on. Then again today on some urban driving the temp gauge shortly acts up and check engine light is on. Jeep works fine and temp gauge recovered quickly from it's misadventure.

What do you guys think, I'm leaning into bad wiring. That is the next to check. I also though it might be good to refresh all the main grounding cables.
 

FinKJ

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It might prove useful to someone to update on this. Issue solved. First replaced the sensor. What was left was error code and check engine light when revving the engine close to red line.

The cable bunch that the coolant temp sensor in part of is mounted on top of the engine in a bracket. This bracket was loose from the end that had the connecting cables to the coolant sensor. This may have caused the cables to resonate or move when high revs and causing pull on the sensor cabling . Fixed the mounting and improved the cable protection a bit. No issues since.
 

Ksat

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Sounds like some bad wiring somewhere or the sensor's plug isn't making a good connection ( contacts are loose/corroded). It wouldn't hurt to take a resistance reading it on the sensor itself, too. You should get around 8-10k Ohms at around 75 degrees F and a little less than 1k Ohm when the engine is warm.
 
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