Need help with door locks, passlock + alarm, and dome lights

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mr1mrwun

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Ok I have a somewhat major problem I'm getting prepared to start trouble shooting and need some help on where to start. This may wind up being long so bare with me......I like to be thoro. I've been having these problems since I bought my '99 Yukon Denali about a month ago (and apparently so did the previous owner). At this point all i really have done is checked the fuses which are good. Now that the weather is breaking it's due time I do something about all this.

First let me describe what is happening:

Door locks: completely inop. DS, PS, and barn door switches....no response. Haven't checked the relay yet, but will soon. Don't hear clicking from it being energized from the switches. Kind of suspecting that may be the culprit but let me know if I should look elsewhere. Also the I'm thinking the actuators in the front doors need to be replaced b/c the interior latches are difficult to manually operate. Rear doors are easy to work.

Dome lights: courtesy lights (on the doors) work. Fuses and bulbs are good. Don't come on with the door open or the dimmer switch. DS door switch missing (no brainer for that). PS door switch inop for all lights. Rear doors and barn doors make the courtesy lights come on.

Passlock and alarm: First off I know there is some type of aftermarket alarm on my truck. Second I do not have the key fobs for the door locks. I will post pics of what I've seen. If anybody can give insight as to what it actually does would be highly appreciated. All I have to go on can be seen in the pics. Tried google a few good times and came up with nothing. I removed the card/chip or whatever and my truck still starts up fine. So without climbing under the dash I can only assume the previous owner had it disabled or disconnected someway. Here goes the pics of it.
EA86838D-D6B6-4B19-94BB-C41FA6B032DC.jpg329BF5E4-9CA6-4F25-8BD8-5BD4DE81E10B.jpg27F5F56E-E2B2-41D1-BE73-0BB61CFA4000.jpg4D222396-042F-48C2-ABF5-21EF7F1DF54A.jpg
On to the passlock and/or stock alarm. If I open any of the rear doors WITHOUT the key in the ignition; the alarm goes off (parking lights, horn, and red LED in front of cup holders in center console).
If I close any of the rear doors (after turning the truck off) WITHOUT the key in the ignition; the parking lights flash and horn honks as if I have armed the alarm with a key fob, as soon as the last rear door has been closed. If I go to start the truck after that happens, Passlock I have to sit around and wait the 10-30 mins needed for the passlock to reset itself. I spoke to the guy at the shop where I've had previous alarm/remote starters installed on other cars and he said it sounds like I might have a bad BCM, but he wasn't sure and said i should take it to the dealership to have it checked out LMAO.
Aside from that I've learned over the past month that I need to either put the key in the ignition and turn it to ON or start the truck before opening/closing any of the rear doors.

Now on to the questions!
I know my truck isn't new enough for dam near all the separate systems in the truck to "have" to communicate with each other in order for them to work right............so I'm guessing that the door locks and the BCM talk to each other. And from there the BCM talks to the Passlock/alarm (factory)??? If so should I go ahead and iron out the known kinks before looking deep into either of those modules? I am simply assuming that the previous owner disabled the front door ajar switches b/c they didn't have key fobs to disable the factory alarm/passlock????? Idk but I'd like to have some type of game plan before I start tearing into my truck. Thanks ahead of time!
 

SunlitComet

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One of the two circuit breakers on the fuse panel may broke that would effect all lock, can screw up windows and seats as well.

They alarm thingy is just a disabler that gets activated unless the electronic key is inserted.

Fix the front door light switches first before going any further. You might find it might work properly them as all but the drivers door have parallel wired door jamb switches all on the same set of wiring to bcm. when open the switch grounds a circuit to the bcm so if the switches are missing are broke in an open circuit state they will no trigger correctly. the drivers door has it own circuit as well. Sounds like it is doing what it can with what is working. Read your owners manual for all the details on what it does and when.

---------- Post added at 08:50 PM ---------- Previous post was at 08:45 PM ----------

Oh and the bcm does not really talk to the pcm in the sense of communication over the serial data bus regarding vehicle contents alarm but the passlock computer does.
 
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mr1mrwun

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Thanks sunlit, I'll have to look at the circuit breakers, but the windows and seats work fine. Mirrors too lol. So I will order some new door ajar switches and take it from there and report back. Thanks again.
 

SunlitComet

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if those are good then power is available to the locks when routed thru the DPDT actuator relay. However the power from the door switches to control that relay is fed from fuse 13 CIG LTR. Is that socket working? It would be the center one that does not have a flip open cover. if that fuse is dead it can keep the on-board audio amp from working(if optioned) and would cause a "no communication" issue with scanners.
 
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mr1mrwun

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I will check that as well. Just to be clear are you talking about the door lock relay under the dash above the gas pedal? And sorry you lost me on the fuse.....you mean the fuse box under the hood?
 
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mr1mrwun

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Rodger that. Your discrip threw me off lol. Thanks again.


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