I have a 2000 Bonneville and I had the service engine light come on a few days ago. According to Advanced auto parts, It was an improper coolant temp(low). I replaced the thermostat and sensor. I tried to disconnect the battery to clear the codes but it didn't work. I know that Advanced will clear codes IF you buy the part there. I did not. Please help me guys. Thanks.

O Reilly will scan and clear the code for free.

If your problem is truly fixed it'll go off on its own within a couple of days.....

Likely this one, https://www.gmforum.com/showthread.p...66#post1390948 With a new thermostat it should reset. If you don't want to wait, disconnect the negative cable for 20 mins. That should reset it.

Thanks guys for the info. After about 5 drive cycles the light went off. Now on to problem #2.....