1999 Chevy Blazer immobiliser prevents vehicle starting

TOM.BERRY

MEMBER
1999 CHEVROLET BLAZER
6 CYL
4WD
AUTOMATIC
49,000 MILES

Hi there,

I had an intermttant immobiliser problem that has moved from inconvenient (would not allow the engine to start for 10 mins after stopping the engine running) to down right 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 immobiliser.
I have been told that it is possible to re-wire it so as to disable the immobiliser. 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 immobiliser/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
Many thanks in advance.
TJB

2 Replies

MERLIN2021

MECHANIC
17,250 POSTS

Have you done 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 "off" and wait 5 seconds
Repeat 2 more times for a total of 3 relearns.
Turn key off, then start it

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Saturday, June 12th, 2010 AT 9:59 AM

TOM.BERRY

MEMBER
4 POSTS

No I have not attempted the relearn procedure, but before I do woul dyou please answr the following:
1) why would I need to if Ihave not changed any of the relevant components? According to GM data it is only necessary after a module replacement has taken place.
2) according to the instructions the wait time of approx 10 mins is governed by the security telltale light going out, but the lamp on my vehicle always etinguishes after 3 secs - which implies that the prolbem is not to do with the PASSLOCK process.
3) there is no reference anywhere to the red LED that is located in the dashboard next to the hazard warning button. Is this a UK market specific?
4) there are 2 emergency manual override procedures, one is listed in the manual that uses the rear fog light switch, and there is another specified on the red Texalarm card that references the red LED. I've tried both with very very limited success - more miss than hit in my experience.

The vehicle started first time this morning. Then after turning it off and leaving it for about an hour I tried it again and it started OK, but when I tried it again the 3rd time it was a non-runner again. I can't use it because I can't risk getting stranded somewhere.

I really would like to rewire the ignition to bypass all the immobiliser circuitry because it is far too complicated for it's own good.

I subscribed to the Alldatadiy. Com yesterday and have printed out some of the diagnostic tables to start some problem diagnosis, but of course I don't have a scan tool to be able to check the DTCs which makes life a little bit awkward, so I'll just get as far as I can.

I'm also going to take off some of the under-dashboard panels to check the wiring connections to the modules in case it's something basic like loose connector or earth strap.

Your feedback on the above questions would be greatly appreciated.

Regards,
TJB

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Sunday, June 13th, 2010 AT 6:25 AM