use key in door lock and set off alarm?

00jeepxj

Original poster
Member
Nov 23, 2018
3
michigan
Greeting all! I am wondering if some of you wise folk can point me in the right direction to fixing this issue. I have a 2003 trailblazer ls with the auto 4wd system and when I put my key into the driver door lock it will set off the factory alarm system. If I use the key fob it works just fine and doesn't set off the factory alarm. I am new to having a vehicle with this much electronics in it as my jeep has power mirrors as it's only option and just one computer for the whole thing. Any guidance to point me in the right direction would be much appreciated.
Thanks!
 

Drec

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Supporting Donor
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Jan 29, 2018
216
Yakima, Washington
I don’t have an answer to your problem, but see the same issue with my Envoy sometimes. It happens about 1 out of 10 times with my car. I just use the FOB to shut off the alarm.
 

00jeepxj

Original poster
Member
Nov 23, 2018
3
michigan
glad to know that i am not the only one. It happens all the time with mine. I am at a loss as to how it would set off the alarm unless there is supposed to be some kind of a sensor that is attached to the lock itself that i don't know about. When I did pull the door panel off to find a strange clunk ( honest to god it was a flashlight on the brace going across the door) I looked and didn't see any kind of a loose wire or a place for a wire to attach to on the lock cylinder.
 

Drec

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Jan 29, 2018
216
Yakima, Washington
I stopped using the FOB after having another problem with mine; which I mention on another thread. I would use the FOB to lock the car, then I’d go out and the car appeared to be dead. I’d open the car with a key and then the key wouldn’t come back out of the ignition. I’d disconnect the battery and everything would reset and work correctly.
 

Chickenhawk

Member
Dec 6, 2011
779
Replace the drivers side door lock actuator. AC Delco 11P4.

The sensor doesn't get used much as most people use the fob, so the contacts get corroded. So until you replace the actuator, make sure your interior dome light switch is enabled, and every time you insert your key and turn it, make sure the dome lights come on. If they don't come on, then the actuator sensor didn't detect the key properly and the alarm will sound. Most of us just get used to turning the key and making sure the dome lights come on before opening the door.

You can try using the key more to exercise the contacts but this doesn't really work quite as well as exercising the contacts on the 4-wheel-drive switch with the engine off 20 to 30 times every few months.
 

Drec

Lifetime VIP Donor
Supporting Donor
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Jan 29, 2018
216
Yakima, Washington
So if you turn the key, to unlock the door, and the dome light doesn’t come on, the alarm will sound? I’ll have to pay attention to that, I’ve never noticed before Thanks!
 
Last edited:

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
I`m surprised that an LS has the alarm!
 
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00jeepxj

Original poster
Member
Nov 23, 2018
3
michigan
You were spot on about the dome light trick! Tested this out in the morning while at work and wow. I now know what I will be having to replace in the near future. I was amazed that i had the alarm as well!
 

Chickenhawk

Member
Dec 6, 2011
779
Glad I could help. When I had the alarm go off a few times, I just got used to checking the dome lights before opening the door. When I replaced the drivers side door lock actuator, it solved the problem for many years. (A bit of a fiddly job with some trial and error the first time, but not too hard.) I have now had it happen again, which is why I say the contacts get a bit corroded when not used a lot. It is just one of those things to get used to on any platform with door-lock deactivated alarm systems.

Interestingly enough, most of our platforms have the factory alarm system. It is listed as UA6 or UA5 on your glovebox RPO code list. Many owners don't even know this.
 

littleblazer

Member
Jul 6, 2014
9,265
I`m surprised that an LS has the alarm!
They all do no? The only options my truck has are 3.73s, cruise and mirror defrosters. (And 4wd...)

I second the dome light trick. I usually hold mine a second before I open the door. Also seems to work.
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
My LS has the alarm. I always thought they all did as well. I think in a decade of ownership i only used the door key maybe 3 times though so never noticed an issue.
 

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