Cadillac Repair: Cadillac deville 1996, cadillac deville, oxygen sensor

Question
My car service engine soon lights comes on and off letting me know I have to service my emission system, and now the car my not restart light has come on, by any means can I get any information on that might help me at all, the dealership says its $325 for them to change the oxygen sensor because one is defaulted by the catalytic converter, but what about the engine may not restart light that which has come on, please any information on this may help thanks...

Answer
The message CAR MAY NOT START is due to a fault in the theft and PASS-KEY system of the vehicle.

Could be:

faulty ignition key chip on key.
faulty wires within the steering wheel key lock cylinder.
fault in the PASS-KEY module.

All need to be tested by special test equipment.