Driving home from San Diego to Vegas last night when the water temp gage slowly started dropping from my normal temp of 205.. 205, 200, 190, 180, 170 all the way to dead stick. Hit the buttons on the digital and it read XXX. Then a minute or two later “check coolant level” then “hot engine turn off AC”. I checked oil temp and it was normal with no signs of rising. I had checked all levels and fluids before the trip. So pulled over and checked the coolant level manually and it was fine, no signs off hot engine. Bubbling, burping, hissing or cracking. When to start car back up and very hard start, didn’t want to fire up. Let it sit for a bit and then it started and ran fine. Started down the 15N for about 5 miles and presto the gage was back to normal reading 205 coolant temp. Another 5 or ten miles and back to “check coolant level” then “hot engine turn off AC” and gauge was dead again. Then back to normal again..This continued back and forth every 15 minutes or so all the way home.. Approximately 10 times…

My questions are;
1) What the hell since there is no level switch to go bad in the 05 C6?
2) What these errors make the car not want to start?

2005 C6 30K miles, procharger, meth kit, kooks headers, mid and exhaust. 575rwhp 520 ft tq.
All mods been on and working great together for over 15k miles, nothing new to cause any problems…

Thanks!!!!!!!!!!!!!!!!!

 

Has any thing occurred that would have allowed air into the cooling system? If not, it sounds like a defective coolant temperature sensor. You may want to use something like a tech 2 to see what signal the coolant sensor is putting out both cold and hot, and go from there. Check other codes as well. Also check the thermostat for proper operation, make sure it is not sticking.

The car may have been hard to start because the ECM thought the engine was cold when it was really at normal operating temp.

There is no low coolant sensor, so the ECM uses an algorithm to determine if the coolant is low or not.

 

Sounds like air in the cooling system or a bad coolant temp/level sensor.

 

I would have thought sensor, but the 05 doesn't have a level sensor.. It uses some mathematical algorithm. Stupid asses at GM. should just use a $2.00 sensor..

 

Anyone??????