Engine code p0118

Black GT

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Sep 8, 2018
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Jacksonville, Florida
Yesterday while driving my 01 GT I noticed something just didn't feel right. While sitting in line at taco belle the engine idle would on its on raise up from 700 to 1100 rpm's. Then it would drop back down to around 500. Car is a manual. This morning I was driving the car and it was doing the same thing. While sitting at a red light at a busy intersection the idle started rising slightly and the the engine shut off. It took about 30 seconds of cranking before it started. It normally starts right up. When I got home I grabbed my scan tool to check the code. P0118 Engine coolant temperature circuit high input. I checked it in live data mode and noticed my coolant temperature would rise to 208 degrees before the cooling fans would come on and then would drop to 199 degrees before the fans went off. My temperature gauge reads normal at the half way mark. Aren't these temperature a good bit above normal? A few minutes later I started the car and it blew out a cloud of blue smoke. Several hours later I started the car to move it to my driveway and there was no smoke at all. I have noticed the last couple of months that while sitting idling for several minutes when the engine reads max operating temperature (half way on gauge} the car emits blue smoke out the exhaust. It while driving the car never emits smoke only idling when the engine is hot. Any input is appreciated. Wanted to add, the freeze frame data from when the code was set says the ECT reading was -40.
 
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wmburns

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Aug 14, 2009
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Wanted to add, the freeze frame data from when the code was set says the ECT reading was -40.
^^^This is the expected results when there's a problem with the PCM receiving a valid ECT sensor signal. This is also what the P0118 DTC is trying to tell you.

Since the ECT value is valid sometimes and not others, this tells me that the ECT sensor itself is likely OK. I would look for a wiring problem between the ECT sensor and the PCM. Think corrosion or poor connector pin fitment.

One way to trouble shoot this is with a "wiggle" test. IE, wiggle the wiring harness while monitoring the ECT value looking for a change.

I checked it in live data mode and noticed my coolant temperature would rise to 208 degrees before the cooling fans would come on and then would drop to 199 degrees before the fans went off. My temperature gauge reads normal at the half way mark. Aren't these temperature a good bit above normal?
For the record the above ECT temperature are NOT high. But if you are concerned double check that the engine cooling fan is actually works on BOTH speeds.
 
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Black GT

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Sep 8, 2018
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Is this the ECT sensor?
 

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