How do I

Is there a way to disable factory anti-theft on '05 Chevy Impala. Dealer said they could reprogram with a 25% chance of fixing issue (check engine light blinks upon ignition, won’t start. Wait 15 secs, try again, and repeat). Apparently anti-theft cycles codes and just have to hit at the right time.

OK, so first you wanted to know how to disable the alarm on a 98 Jetta. Now an hour later you want to disable the alarm on an '05 Impala.

You really are kinda starting to sound like a car thief here dude. As such, you’re in the wrong place.

Yes I understand the thought. My car is a Jetta and when I told a friend at work (who is not very computer inclined) that I was getting good responses he asked me to ask about his '05 Impala. His vehicle runs but he has issues. My vehicle does not because when I attach a battery (car has been sitting for 18 months while I was in the service) the alarm goes bonkers and nothing turns it off. Kudos for your cynicism but one would think that a “professional” car thief might have more resources than a public radio show forum. Think? I don’t know but I imagine so. My problem remains, and from what I hear, the advancing anti-theft developments are complicated and problematic.

“one would think that a “professional” car thief might have more resources than a public radio show forum. Think? I don’t know but I imagine so.”

Hang around for a while and read. You might be surprised at what kind of crackpots show here asking all sorts of things. Your idea on this, while reasonable, assumes that everyone is running around with all of their marbles.

Tell your friend the next time s/he has the time to put the key in, turn it to run - that spot where all of the dash lights come on, but before it cranks over. Leave it in the run position for 10 minutes. Then, without turning it back off, crank it up. I cannot tell you for certain that this will do anything. But some past internet searches have told me that this is a way to reset the GM security brain.