AggieJustin

Yeah, you're right.

That's what I get for thinking at night. The ECM checks the ECT as a parameter for high idle, but it is primarily driven by the IAT.

bent valves

I tried pulling the coolant sensor connector to get the three cylinder high idle but it doesn’t work. I think the ECM is too smart to allow an open connection to the sensor to work. My truck set a code, but with enough Crown Royal the high idle doesn’t matter either.

Red Goat

Back on the coffee again!
That other stuff just works temporary

Did anyone happen to take a look to see how the temp guage ties in to all of this?
In other words could it be reading normal because of its own ground?
Also I will have to phone him tonight and get an update.

AggieJustin

The best place to start would be with the driver's side battery ground post and the grounds to the frame rail from that post. This is where the ECM is receiving it's ground from.

Otherwise, you would need to get a meter on that ECT sensor and check the readings against the values provided in this thread. Even better, if you could have someone reading the values from the sensor while cranking, that would give us an idea of what the ECM is seeing while the starter is engaged.