Alarm and BCM
 

Hello,
I have been having a problem with my 2001 four-door Blazer. I bought it not realizing that the alarm was still functional and I did not receive any key fobs with the purchase. There are two problems with the car:
1. The alarm will go off by itself without anyone near it and the only way for me to shut it off is to run outside and put the key in the driver's door. The Security light in the car never goes off and I've sat there for a good ten minutes and watched it (I don't know what this means) andright beside the steering wheel is an led light that the previous owner claimed was part of the alarm that has neverstarted blinking until today. Is this a factory alarm? How can I tell? Where is the best place to buy a fob?
2. Mydome lights in the car only come on when I hit the manual override buttonnear the headlight switch. My radio will not stay on after the ignition is turned off and my side mirrors won't move with the controls from inside. Also mydriver's side automatic window rolling down mechanism won't work, but the window itself will roll down. Are these connected in any way? Is it simply the BCM (Back Control Module)? My auto locks and all windows will roll down and up? Could it be something else? Thanks for any assistance!

uncthaddeus

RE: Alarm and BCM
 

Sounds like you have a door switch that isn't working properly. I ran down through the check a while back... Here it is: Dome lights/keyles...

As far as the key fobs are concerned, you need to check and make sure that you have the proper RPO code (AU0 - A, U, Zero if I remember right). If you have AU0 on the RPO code list inside the glove box, then your truck is equiped with the RKE module necessary for remote locks. From there you need to find the appropriate key fobs.

One indication of having an aftermarket alarm is the fact that there is an additional LED. The factory alarm only had the security light in the dash, no additional lighting for the alarm.

On the window, for the auto down, you have to hold it until you hear a click. The express down function will "latch in" after 0.31 to 0.8 seconds. I'd have to look at the schematics again, however, I believe that everything for the auto down functionality is in the master switch panel on the driver's door.

RE: Alarm and BCM
 

It is possible that the aftermarket alarm wiring is tapped into a source that is connected to the BCM and is causing this problem. There are indications in the electrical troubleshooting portions of the GM Service Information DVD that I have that have indicated that if some factory functions are not operating as specified to look for aftermarket wiring problems....

Some after market alarm installations will interfere with the installed options only by the fact that they have introduced voltage changes to the circuit and that makes them not function as the factory intended. Then you have to make a decision keep the aftermarket system or remove it to get back the factory functions...

RE: Alarm and BCM
 

Yeah, I can see that causing issues, specifically if on the rear hatch sensor, I think they just tie the signal into the dome lights... That's what one shop told me they'd do... Which, with the curteousy/security light, would make the alarm sound instantly upon arming...

RE: Alarm and BCM
 

An aftermarket alarm, if installed correctly, will not interfere with the use of any standard features. If you tie into door triggers or domelights, or doorlocks, you wire up relays if the polarity is different, and those then replicate the actual car unlocking the door, or opening the door.