Hi I have an 05 grand prix. The key has been broken off in the ignition. I lost the transponder part of my key. Now the car is stuck in antitheft mode.  The car has too many miles and repairs to put much money into it. I'm trying to find a way to just bypass the antitheft or hot wire it. What would ya all suggest I do please?

I would think the cost of a locksmith to remove the broken key and make a new one should not be cost prohibitive (granted it may still costs a couple of hundred bucks for him/her to come out to do the work).

Disabling the anti-theft mode requires the use of a working ignition key.

 

Is the security light flashing when you try to start the car? If so, try performing a "Passlock Relearn":

1. Put the key in the ignition and attempt to start the car, the "Security" light should go on and the car won't crank. Don't move the key to the "off", leave it on.

2. Leave the key in the on position for around 10 minutes, the security light should eventually go out.

3. Turn the key to "off", wait 5 seconds, then attempt to start the car. If it starts, you're done! If it doesn't start, to back to step 1 and try again. You may need to repeat this process up to 3 more times to get the car started.

Try to turn off any lights / equipment in the car while you're doing this to avoid killing the battery.

The problem with that is that I don't have the transponder part of the key

The locksmith (or you or a GM dealership) should provide a new blank key with a new transponder in it. They will have to cut the key and program the key to the car. I would expect the locksmith (or a dealer) to know how to do that. That can’t happen until the old key portion is removed from the ignition.

Find somebody with the "HP Tuners" PCM operating system tune software reprogramming kit. They can disable "VATS" - the Vehicle Anti Theft System.  Around here, that would cost you two HP Tuners "credits" at fifty bucks each - one to license the PCM hardware and another credit to license the operating system inside the PCM.  Then another fifty bucks for the technicians time.

 Its going to cost some money no matter what.  Frosty's idea above is certainly the better and faster way to go.

Rick