The ignition switch is known weak spot on these vehicles. When they fail all kinds of electrical gremlins can occur all. Things from the radio turning itself on or off, changing stations by itself, different lights going out and then coming back on, etc. Normally the ignition switch is diagnosed by ruling everything else out or by how weird the electrical problems are.
Here is a how to on how to change out the ignition switch by yourself:
Okay, I replaced my ignition switch yesterday. I was nervous, I had read numerous posts about this, but some of them conflicted, and I wasn’t sure what I was getting myself into. I haven’t done a whole lot of work on newer car systems, although I did replace the stepper motors on my Envoy a...
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Also, do not cheap out on the new part. Please stay away from the Amazon & ebay parts that are priced in a too good to be true fashion and avoid most auto part stores house brand. "Forum favorite" ignition switches have the following brand names - ACDelco, NAPA Echlin, Delphi, Standard Motor Products (non T series) or BWD *non P series). Also, the cost of the part ranges from about $15 on Rockauto.com to about $40 for one of these brand's switches.
The relevent question for these switches is not if they will fail, but when they will fail. I personally keep a spare one in my glove box.
Good Luck!