Service theft system 2004 grand prix

Question edited. We are not that type of site, and your issue happens to anyone who disconnects the battery or lets it run flat.

Passkey 3 reset is best done by a vehicle electronics tech or an auto-locksmith, but you can try.

https://www.youtube.com/watch?v=pmtFD_y4EY0

Videos and articles.

https://www.google.com/search?q=2006+Pontiac+Grand+Prix%2C+reset+passkey+3

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Its sounds like the anti theft system has failed. This is very common in GM cars. This has happened to me so I know your frustration. There is a site that has a lot of information on how to bypass/ permanently fix it. You can actually do it yourself for far less then what a mechanic would charge. Hope this helps!

deactivation is best carried out at a service /repair facility , there is a process to reset/relearn the system follow this link which gives step by step instructions
How do you reset your anti theft device on 2004 Pontiac grand am

Hi
Here's the link to the Owner's Manual if yours isn't available. It will describe how to reset the 'pass key' system.

http://www.pontiac.com/content/dam/pontiac/northamerica/usa/nscwebsite/en/Home/Owners/Owner_Resources/Manuals/en/us/2004/grand_prix/2004-pontiac-grand-prix-owners-manual.pdf

You need to enter the unique code for your radio that was given to the orig owner. If you do not have that you will need to see the GM dealer.

This car, like most newer cars has a passive theft system. If the car sees a problem with the system when the car is running it will turn on this indicator. When this indicator is on the theft system will not arm until it sees the problem is no longer there. It probably needs a ignition switch but it should be checked out before you toss a new part in it.
I hope this helps. Please leave feedback if it did.

1. wait 10 min with key in start to reset passlock then restart
   

You can disconnect either battery terminal for 15 minutes...then reconnect...this will reset all of the systems...Also, is the Grand Prix in an extremely cold climate? If so, the door jams could have some ice or dirt causing them to send a wrong signal...did the G/P go through a car wash recently? This wash could have supplied the extra ice or debris causing the theft security systems warning light...Great Cars...you should be able to fix this...:)

take it back to garage for a computer diagnostic

If the after market alarm system isn't completely removed from the vehicle and the car restored back to where it was prior to the alarm, the alarm system will think someone is trying to steel the car and has shut down the signal from the PCM.
The alarm needs to completely removed.
Once the alarm has been removed, I would use a GM ignition key, you may need to tow the car to your local GM dealer to make a new ignition key and program the key to match the PCM, it's possible the vehicle ant-theft system has shut down the electrical because of the incorrect ignition key.