I have a 1996 Civic that is repeatedly throwing code P0118 Engine Coolant Temperature (ECT) sensor circuit high input shortly after starting the car. But the temperature gauge works fine.

This started after I had the transmission (manual) changed so I suspect something did not get reconnected, but the mechanic cannot find anything.

This was also the first time using this mechanic (chain) since the one I went too since I was a teenager went out of business.

Any thoughts on exactly where to look when you get a P0118 but the gauge is still working fine?

Thanks

 

The gauge has nothing to do with it. This is the ECT and testing:

https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/ect-o2-running-rich%3Dbad-mpg-2618622/

 

As Hero says, the temp gauge in the cluster uses a different temp sensor -- the 1-wire sending unit under the distributor.

The 2-wire temp sensor (ECT sensor) under the distributor is the one you need to focus on.

 

Thank you both for your replies, today was the first day I had to look at it.

Following your instructions found the ECT under the distributor.

Anyways tested the ECT with OHM meter, 1699 cold, and in range of 200-400 when warmed up. So it is good.

Tested the voltage as indicated, red/wht >> grnd = 5v, red/wht >> grn/wht = 5v. From there the diagnostic page in the link says to substitute with a known good ECU, which I do not have.

Would there be anything else I can try other than going to a dealer?

P.S. I already changed the coolant and bled the system as a post somewhere had said dirty/low coolant could contribute to a PO118 code.

 

If you reset the ECU, does the code return? If so, then the ECU may be bad.

 

this is the kids car and I hadn't gotten to try resetting the ECM yet, but the check engine light went back off on it's own now. Nothing changed that I am aware of other than the weather has gotten cooler and more seasonable.

So the light is off and I am just going to hope it stays off. If it comes back on I will try resetting the ECM.

Thanks again for you help.