When there is heavy rain my car through this code p0118 .Pcm or wiring issue?

 

You should start with the sensor and check the connector.

Have you ever disconnected the PCM. (BTW - you should not unless absolutely necessary.)

 

Nope have not touched the pcm.The connector looks good and I cleaned the sensor,I will have to wait for the next down pour.......to see if the code comes back again .

 

What coolant temperature does the car read when this happens?

 

Below 160 and the car runs like **** when it dried out the car was fine.

 

Makes sense: http://www.wellsve.com/sft503/Counterpoint2_2.pdf

If an incorrect coolant reading is coming back, that will throw off the car. If the connector is good, I'm wondering if the sensor is cracked or something like that and letting water in.

 

Could be a new sensor is need ,its located at the front of head behind the abs block hard to get it wet but anything is possible.Good article the coolant temp sensor can make you car run rich burn a hole in you pocket.

 

Yea, Wells has a whole sequence on newsletters on sensors, which are generally really good. I've bought a lot of their sensors, with various levels of success. Some were good (coolant level sensor) and some were god-aweful. (oil pressure sensor - via Duralast)

I recall seeing similar threads where these weird happenings were due to water getting in to the PCM connector. The catch is that once you open that connector, you are getting in to a whole new bag of worms. GM issued a TSB that says that anytime you unplug the PCM, the connector seal needs to be replaced. (So, if you go that route, you'll want to have another seal handy for when you put it back together.)

Any chance that a previous owner may have unplugged the PCM?

Before you start guessing with the PCM connector or a new sensor, maybe you could try some tests:
- Measure the coolant temp sensor (as demonstrated in the Wells article) in a good condition and then again when you are having the problem. If it measures good in both cases, that would rule out the sensor. You'd just want to make sure the car is up to temperature for both tests.
- Spray the sensor down with some water and see what happens. (Probably best to avoid drenching the rest of the engine.)
- Spray the PCM connector down with some water and see what happens.
Maybe you can test the resistance on the coolant sensor If you can't see any cut

 

I brought the car in 2001 from the orginal owner and the car had major guard warrenty unless the dealer removed it. I wouldn't water test the pcm to many things could go wrong the coolant sensor I will buy if it happens again.