GM ignition key readers

[Terry Martin]

Craig Pugsley wrote:

> Do the GM car keys with electronics inside them that the ECU talks to
> still just use resistors inside the key or have they changed to something
> more secure (ie something electronic in the key)?
> 
> If so, when did they change?

Ron Tyler <dcmckenna at worldnet.att.net> wrote:
Just resistors. There are 15 possibilities and they range from
400 ohms to almost 12K ohms.
& What spurs your interest on the VAT system?

Sorry to disabuse your notion Ron, but Delco has come out with more
vehicle anti-theft systems than they can remember.

Starting as a running assembly line change on Vette's in late '85 &
officially '86 they introduced "PASS-Key", which is what Ron is
referring to. They progressively implemented the system in various
vehicles, and came out sometime later with "PASS-Key II", which is
similar. They have also introduced "PASS-Lock", which utilizes a Hall
effect sensor attached to the ignition lock cylinder, with a activating
magnetic embedded in the lock plug in various Yr& Models. There is no
interaction with the key. They have introduced PASS-Key III, which
utilizes the technology I believe you are referring to, which has an
embedded transponder in the key head. It has appeared in late model
products as a running assembly line change, and is the same technology
as that used to tag animals. It's basically a proximity detector which
provokes a digitally encoded response from the embedded transponder in
the key head. In some of the vehicles there is also a "Universal Theft
Deterrent", installed on practically a random basis, which is a factory
alarm system. If the vehicle has remote locking capability it probably
has the UTD.

Terry

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