Update-2 on Thermostat and Service Engine Soon Light

Was looking last night at the big hose connecting on the throttle body end. It wasn't quite all the way on. I believe this is what tripped the light and gave me the code P0101.

I also found last night a little write up about the 3.5L and thermostat. I'm having these exact same problems. Anyway, I purchased this today and will put it on this weekend, I hope.

If anyone has any experience with this please let me know. I was told at the dealer that you can't buy just a thermostat anymore. You have to get the whole housing. Its a redesign, which makes sense. I'm not really sure what this is going to take to install. Hopefully not to bad. If anyone has done this themselves, please let me know.

Hope my experience has helped someone.

Matt

Hey Matt,

I have a '99 with the 3.5L. I also have the '99 factory manual. It indicates that changing the thermostat is not a big deal. The dealer person was right, the thermostat is integral to the water inlet housing. You need to drain your coolant, then remove the three hoses, two bolts and it should pop out. They say to clean the surfaces, and to use RTV sealant on the bolts - and install in reverse order. I am not entirely sure what RTV is but the auto store folks should know. They list a caution regarding the coolant. As you may know it is a specialized -some say in a bad way- coolant. So if you need more get it from GM. I believe it is called Dexcool.
Best of Luck