ive read a few articles on here about what im posting but nothing that really helped me out..my vehicle is a 1998 chevy blazer .over the last week i replaced head gaskets and all gaskets above .after buttoning everything up it started right up with a couple of minor issues a loose rocker that had a minor tap and a small gasket leak at the manifold ..so yesterday i tore down what i needed to to address these couple issues ..thats when my trouble started i went to fire it up and security light was on solid ive never had a vehicle with this option as ive always owned a truck an older truck ...my other is an 84 chevy 3/4 ton...so i searched the net for something on the passlock system.and tried the relearn sytem over and over ..to no avail..the light never flashed ..i attempted the bypass ...again nothing ...i also read something about taking my obd scan tool and clearing out any security code that may be present ..but the tool circulates thru and cant detect protocol is what it shows ..not being familiar with this system ..im at a loss as to what to check from here or if my issue is part of a larger problem or something simple that ive overlooked and am un aware of any help is greatly appreciated

 

I just had this exact samething happen to me. I did my heater core and didnt redo all my elec connections correctly...the main block under the glove box wasnt seated all the way. I hate to say it but you need to go back over all your connections that you touched or were near. I would start with thee ones related to the pcm....the connections from that to the truck are not complete...thats why the scanner wont work. Mine did that to.
Good luck...its a pain in the a$$ but you need to check and double check again.

 

ive checked everything over and there doesnt appear to be anything amiss...is it possible that i may have somehow shorted something out..im going to go out and go over everything again just for the sake of it...so i can say 100% i didnt miss anything.i appreciate any and all input on this issue

 

ok so ive checked all connections fues ect. and still the same thing no read on scanner and security light staying illuminated. i think im about ready to push it out into the road because it should be something simple that i cant seem to find yet

 

Is it possible that my ecm went bad.is there a way to determine this

 

did you pull each connection apart and put back together or just a visual check.
it could also be a pinched wire. i know its frustrating but its in something you touched. most likely if the ecm was fine prior to work then it still is fine.
i dumped three full days and a trip to the dealer into mine...wasted a week on a simple stupid problem. i hate electrical problems above all others.

 

I went over every connection physically tested all fuses relays and even found some I didnt know were there there was a short instance when the lights began flashing with the key off.. Headlights and dash lights ..the security light stays on no flash whatsoever also the dome light and if you push the lock button with the key on the driver side door will not lock..the plugs I removed before thos happened were forthe ac plugs the two plugs for the maf sensor and the center block from the fuae box on the driver side fender I have power to all relays and plugs

 

a relative of a coworker today told me that my problem is a body control module or bcm has anyone else had a problem with this or does this sound right..i googled it and i read something about they lose there memory and then cant communicate with the ecm and that the bcm also controls the immobilizer or the security feature..again i apologize im not real up to date with these newer vehicles and the technology

 

The bcm is located under the dash behind the the ash tray area....if you didnt do anywork in the cab i dont know how you could have done anything to it. I know there us a cluster of relays behind the left side of the gauge cluster way up in the underside of the dash....you could check them. They are hard to get to but it can be done....maybe check them. They panel they are in can be unclipped and dropped down. Tight area though.

 

im not sure myself the guy that told me to change it out is the head mechanic at a chevy dealership..i havent done anything to it yet im just kind of leary about unplugging anything alse at this point. other then what i know. ive left the battery unplugged for a day now and ive got the same thing. i think im going to walk away from it for a day or so and just try to get some insight on it. sometimes a clear head makes for a new perspective..i do appreciate all your insight youve given over the last couple of days as well..im always open to new suggestions or ideas..sometimes u just get so frusterated a fresh perspective is what it takes to get it done