Driver Unknown on 1999 Buick Park Avenue

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Shut off the car, got back in started the car up and it would not start. Unknown driver appeared on the dash. What could be the problem?
(3) Answers
If trying your spare key does not work, chances are the fault is with the Passlock sensor. For more information please read the RepairPal article on GM Passlock anti-theft systems, here is the link -
It sounds like a problem with the anti-theft system. The system may not be reading your key correctly. If you have spare key, try it and see how it works.