GM ignition key readers

[Terry Martin]

dzorde wrote:
> 
> I've seen an article (can't remember where) that talked about a rolling code
> facility for automotive key entry. The chip was powered from a coil loop
> which received power from another coil around the lock.  It would then Tx a
> code to the ECU via the lock coil.  It utilised the rolling code facility.
> As to whether any car manufacturers use them ???
> 
> Dan     dzorde at geocities.com

There are at least three different variations of the transponder
equipped system domestically, of which the rolling code concept is one.
Another uses fixed codes with 10 keys total. I believe three are
supplied with the vehicle, and the factory holds back seven. If you are
dumb enough to lose all 10, you have to have the entire system replaced.
The third utilizes a progammable controller, and new keys can be added
and others deleted with a simple programming procedure. I think Ford
uses this one, and they screwed it up big. It turns out that if the key
being removed from the system is tried in the ignition before the
programming cycle times out, it reprograms it back into the system. I
think they first used it domestically in the '96 SHO.

Terry