Digital Temperature gauge in a 2000 Pontiac Bonneville has gone bad. How to and how much to fix it?

Question

The numbers still light up, its just that the temperature is off by roughly 20-30 degrees.

Answer 1

I'm afraid I've never been in a Bonneville...but I'm guessing the guage design isn't much different from a Grand Prix.

First question:  Is your guage capable of switching between F and C?  If so, is it on the one you prefer?  Farenheit's numbers are considerably higher than Celsius.  I don't know the exact calculation but you can find that info with a Yahoo! search.

Second question:  If the first question did not solve your problem, then is your guage joined with the instrument cluster or the car radio?  I would first guess that there is a problem with your external temperature probe (and that I have no idea how to diagnose, repair, or replace) but if that is fine then you would have to go on a certain auction site, find a junkyard, or spend five times as much and buy it at the dealership.

In the end if this problem is absolutely unbearable and none of the above solutions fix your issue then you're going to have to make a trip to the dealership.