1999 Chevy Blazer 4 wheel drive auto immobilizer

[jdetty]

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.

[ProTech]

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.

[stillfishing]

On a 1997 Blazer it was stuck in 4 wheel drive, found that the actuator has vacuum to it all the time. I unhooked the vacuum line and plugged it off. it is in 2 wheel drive now, but the 4WD light is still on. Also I think the shift points are too high, it shifts between 2500 and 3000 rpms.

[carriedi]

check that the axle is really disengaged from the 4wd solenoid. if the axle is not locked in 4wd then you have a short or a bad switch in the front axle.

do you have a check engine light on?

[stillfishing]

there is no check engine light on. it is disengaged, i was going to take out the vacuum switch on the transmission or transfer case and see if it is stuck. what solenoid are you referring too, there is a cable that engages the front differential

[carriedi]

there should be a switch in your front axle that tells you when the axle is engaged. look at where the actuator is (the part that locks the axle in 2wd or 4wd) the switch is #13. that should be what lights up the 4wd indicator

[stillfishing]

I disconnected the wiring to the switch on the front differential and the 4WD indicator light stayed on.

[carriedi]

so it says that you are in 4 high, 4 low?

the light is turned on by the transfer case shift control module. Tan/black wire to 4wd high and purple/white for 4wd low. The module supplies ground in these wires to turn the lights on. the switch supplies power to the transfer case module to tell it what mode you have selected. so, power on the dark green/white wire from the switch is for 4wd low, goes to the C3 pin on the transfer case module. Power on the dark blue wire from the switch changes to a dark green/white wire to pin C4 on the transfer case module is for 2wd high. power on the gray/black wire from the switch is for 4wd high.

check to see which out of the switch is powered up to see if the module is getting the correct signal from the switch