Thanks very much to everybody for the details on how to disable this Passlock system. It's an Olds Intrigue, not a Chevy, but this is a major common GM problem that GM refuses to accept responsibility for. Neither the dealer nor the company would cut me a break despite this being a major design defect. They wouldn't even acknowledge it's a problem. Cutting the yellow wire with the engine running and inserting a toggle switch worked and I saved $500.
Added bonus: since the theft system is now disabled, there's a better chance somebody can steal my car. Please do! I won't have to deal with the next GM design problem that crops up (Passlock in the third, following frequent wiper motor failure and a seized AC compressor at 30K miles.) Life-long GM owner, but this is the last.
Thanks again.