Engine Temp gauge wont move

[Mbower]

My gauge will not move, and a new light came on that I have never seen before it says contact dealer with a big x. Does anybody know what this is? I think it has to do with the thermostat.

[Mbower]

Found my answer.

[GeoffA]

???

What was it?

[Mbower]

Found it in another thread.

Actually, I don't think it's the tune. I believe it's the thermostat causing the problem. The cheapo Mr. Gasket stats leak too much coolant by and don't allow the engine to warm up as fast as the stock thermostat. Your engine warms up much slower than the computer likes and it throws this code. A proper 160 or 180 stat will stay closed until the temps allow them to open. Engine warms up faster like stock.

I had a customer with the exact same problem. We lowered his fan settings with the tune, but it did not help. Replacing the stat with a better version that didn't leak cured the problem.

[Chevelleguy]

Hi guys. New to the site and appreciate all of the great info. Last July I purchased my 09 G8 GT with 49,000 miles and love the car. Have had a few issues that took a while to resolve and one was the same as Mbower. I found plenty of GM cars and trucks having the issue of the engine temp gauge and AC quit working at the same time but there were no definitive solutions. There was a definite link between the temp gauge and AC compressor and a possible link to a bad tire pressure monitoring sender. Replacing the tpms sensors eliminated that area as a contributor to the issue. I replaced the temp sending unit with no result. As with Mbower, replacing the thermostat solved the issue. Visibly, the old thermostat looked OK but closer inspection revealed some damage to the rubber seal on the radiator side of the stat. Coolant was leaking by a a rate just enough to slow the warmup process enough for the computer to sense a problem. During the warm / hot summer, the issue almost went away but returned with regularity the first cool spell. Disconnecting the battery would always reset the system and things would be fine for a day or so. It took a while to figure this out as most websites clearly stated the problem, but offered no workable solution. Y'all were on target with this one. Problem solved for me. I have replaced a "wobbly" vibration damper and the tpms sensors. I plan to replace the front hubs today to hopefully eliminate a slight vibration at 65 - 75 mph. If successful, this will be a near perfect fun ride!

[-Ray-]

Hi guys. New to the site and appreciate all of the great info. Last July I purchased my 09 G8 GT with 49,000 miles and love the car. Have had a few issues that took a while to resolve and one was the same as Mbower. I found plenty of GM cars and trucks having the issue of the engine temp gauge and AC quit working at the same time but there were no definitive solutions. There was a definite link between the temp gauge and AC compressor and a possible link to a bad tire pressure monitoring sender. Replacing the tpms sensors eliminated that area as a contributor to the issue. I replaced the temp sending unit with no result. As with Mbower, replacing the thermostat solved the issue. Visibly, the old thermostat looked OK but closer inspection revealed some damage to the rubber seal on the radiator side of the stat. Coolant was leaking by a a rate just enough to slow the warmup process enough for the computer to sense a problem. During the warm / hot summer, the issue almost went away but returned with regularity the first cool spell. Disconnecting the battery would always reset the system and things would be fine for a day or so. It took a while to figure this out as most websites clearly stated the problem, but offered no workable solution. Y'all were on target with this one. Problem solved for me. I have replaced a "wobbly" vibration damper and the tpms sensors. I plan to replace the front hubs today to hopefully eliminate a slight vibration at 65 - 75 mph. If successful, this will be a near perfect fun ride!

Thanks for posting.