03 Grand Prix starts and runs, but security light flashes

[dwilson4421]

My 2003 Grand Prix was having ignition switch issues so it was changed and now the car starts and runs fine, but the security light flashes the whole time you're driving. Needless to say this is very annoying! The relearn process does nothing and there are no codes registering. HELP!

 

[Fivefingerdeathpunch]

Try another key and see what happens. Try the relearn with another key.

 

[waupachino]

Long story short, there is something wrong with the PK3 security system. Read this thread, never did figure out what exactly the issue was. Ended up unplugging the theft deterrent module and the light quit flashing.

http://www.grandprixforums.net/threads/103808-Security-light-flashing