1999 Chevy Blazer 4 wheel drive auto immobilizer

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Joined: Thu Nov 08, 2012 12:24 pm

1999 Chevy Blazer 4 wheel drive auto immobilizer

Unread post by jdetty » Thu Nov 08, 2012 12:38 pm

I had an intermittent immobilizer problem on my 1999 Chevy Blazer that has moved from inconvenient (would not allow the engine to start for 10 mins after stopping the engine running) to downright annoying (2 days in a row will not allow the engine to start unless I leave it in excess of 4 hrs to reset).
When I turn the key in the ignition, all usual dashboard ligts come on, then when I try to start engine all lights etc go out, no starter, nothing.
As soon as I release key back to run position all lights etc come back on.
I have a UK spec vehicle with the factory alarm unit.
I don't normally use the alarm, just lock the vehicle with the power lock button on the door.
Clearly there is something wrong with the immobilizer.
I have been told that it is possible to re-wire it so as to disable the immobilizer. I have fitted car alarms to a number of vehicles, and am competent at electrics, but I don't have a wiring diagram or the knowledge of the immobilizer/security system. Is this something you can assist me with?
I have had the vehicle from almost new, it's really useful for luggng loads, even used it once as an ambulance for my father in an emergency, and apart from this problem it's totally reliable, so I would hate to have to get rid of it.
I Have tried the a relearn on the pass-key:
GM PASS LOCK RELEARN- Ignition to run position, try to start and let key return to run position
Approx ten minutes security light will go off
Turn key and wait 5 seconds
Repeat 2 more times for a total of 3 relearns.
Turn key off, then start it
It started for a couple of days and now will not at all. I have let it sit for almost a year now and tried put a new battery in it and still nothing. Please help
We have replaced the fuel injector and did a complete tune up and the egr valve on the air intake.

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Re: 1999 Chevy Blazer 4 wheel drive auto immobilizer

Unread post by ProTech » Thu Nov 08, 2012 8:20 pm

You can not defeat the immobilizer part of the security system by wiring around it, or rigging up something to bypass it. Sure, it probably can be done, but just let me warn you that always causes more problems than it fixes. We cannot recommend doing any bypassing of the factory components on this site. As for your problem, though, getting the security issue fixed is relatively easy if you have some tools and experience. To fix this you need to replace the ignition lock cylinder housing. The housing is what actually carries all of the 'Passlock' functions on your vehicle. You do need to disassemble the steering column down a ways to be able to remove the housing. The steering wheel has to come off, as does the multifunction switch and SIR coil. Not very involved if you've ever worked on steering columns, so it should be an easy fix. You will have to do a re-learn once again for 10 minutes after replacement and then you will be good to go.
GM Dealer Technician For 18+ Years
In the automotive industry for 20+

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