Yes, only when it is not running. I just recently purchased this vehicle so don't know too much about it's history but the ignition cylinder was replaced already. I do not have the keyless remote for it. If when I bypass the passlock system with a resistor and the light still comes on then Ill have to take the dash bezel out and put some black tape over the light, unless someone has any other ideas. Thanks

 

This happens if any door is opened?


George

 

Yes, this happens when any of the four doors are opened, but does not happen when the tailgate is opened. The security light goes on when any of the doors are opened and it stays on until you close the door. This happens with the key in the cylinder or not in the cylinder, but it dos not happen when the key is in the on position or when the vehicle is running. When the key is in the on position or when the vehicle is running the security light goes off. This is really a nuisance because when I am out camping or hiking with my dog, any time the door is open the security light is flashing. Maybe I am preparing something, trying to think, or making coffee, and this bright red security light is flashing in my face, warning me of a problem that doesn't exist. I often sit in my car to read books - the door is open and there is no way to shut this security light off unless I close the door or turn the ignition on, but that would drain battery. Yet I need to keep the door open so that I can keep an eye on my dog outside, or when it is hot out, keep the doors open to enjoy the cool breeze or air out the car.

I see from the wiring diagram that this all ties in at the BCM, so what I am doing is supplying an additional ground to the BCM through the door jamb switches. I have no idea why the BCM would be bad but I see that 1998-2000 have the same BCM, so I could swap it with the original BCM out of my 98 Blazer to see if that makes any difference.

 

According to your 99 owners manual and my 2002 shop manual this is the intended operation. The security light comes on when you open the door with the ignition off as commanded by the BCM/CTD system. So yes the door jamb switches trigger this. The hack would be to ground/unground the door jamb switch inputs to the BCM. The door handle switches may also be involved. The only impact that I can think of is that the interior light will not come on when the door is open. The security light its self is controlled by a class 2 data line input to the IPC so the only way to defeat the lamp is to surgically remove it from the IPC or cover it. I have never opened an IPC so I don't know how hard they are to hack. Defeating the passlock system with the resistor hack will not change this operation.

If you want, we can check for a parasitic battery drain as a separate issue.


George

 

My 98 and 04 do not do this - security light does not come on when I open the door and goes off immediately after vehicle ignition. Also, no dome light or interior lights comes on when I open the door. I thought this was unusual so I looked in my 98 and 04 - same thing. No interior lights come on when opening the door.

Door handle switches are not involved. Security light goes off when I press in the door jamb switch. So probably the best solution is just to disconnect all the door jamb switches? They just pop out so I can just unplug them.

 

If they come out that easily then yes that’s the quickest “fix”.


George

 

I've attached the first section of my 1999 service manual on the Theft Deterrent system. Perhaps this will help.

The manual also has a list of checks depending on the specific DTC (trouble code). I forget if you have any of those. I can scan the pertinent pages for that and post those too.

 

Thanks Christine that's good information.

George

 

Thank you. I will look over this. I forgot to mention that my coder reader will not read the codes on this vehicle. I don't know why. I only have an inexpensive Autel OBD2 scanner from Amazon but amazingly it has always worked well reading codes on my 98 and 04 Blazers. On this vehicle it scans then says "unable to read." My tech at the shop I go to has a professional scanner that cost him a few thousand.

The driver side door jamb switch only has two wires (one black). I unplugged and removed it and no more light, so I will remove the other three. It seems to serve no purpose since opening the doors does not turn on any interior lights either, yet all interior lights work fine when manually turned on from the headlight switch.

 

Glad you found a workaround.


George