Check engine light wont reset?

You need to clear the computer with a scan tool. But you still won't pass inspection because the readiness monitors will be cleared as well and must be set to pass inspection. Your Buick must reach normal operating temperature of 195 degrees Fahrenheit within 9 minutes of a cold start up. If it doesn't the check engine light will come on and a trouble code will be set after three times of it not reaching operating temperature within those parameters. There's no way around it! The thermostat must be replaced with a 195 degree Fahrenheit one. Hope that helps! Jim

The weird thing is check engine light came on after a 30 minute drive down the highway. Engine felt normally hot to me when I lifted the hood. Wouldn't the light come on within 10 minutes at first start up if it's not heating correctly?

It has to not reach operating temperature within the parameters for three consecutive cold start ups. Is that the only trouble code you're getting? Hope that helps! Jim

Yes, that's the only code. The car is running just fine, my temperature Guage is in normal range. If I disconnect battery, wait 10 minutes, reconnect battery, wait 10 minutes, will that reset the check eine light? Maybe stay off long enough to get inspection?

No, disconnecting the battery will not reset the check engine light. It must be cleared with a scan tool or code reader. But after doing that you need to drive the vehicle for a few days to reset the readiness monitors. You can pass inspection with one readiness monitor not set. Doesn't matter which one isn't set as long as the others are all set. You must also keep the gas gauge between three quarters and one quarter full for the readiness monitors to set. Hope that helps! Jim