My 1996 Chevy Lumina V6 had a leaking water pump, which I replaced. Afterward, it ran great. Then I misplaced the keys. I located my second key set and continued to drive it until one day it wouldn't start. The dash lights would turn on, but the starter wouldn't turn over. I noticed on the dash a 'Security' light on. I started thinking that the back up ignition key did not have the GM transistor on it. The key set was made from the original keys-ignition and door key- but was not the GM style security key. I searched for and finally found the original set and it started right up. The security system must be set to allow a fixed number of starts and then shut off. Back on the road again.