1999 Yukon Denali power lock issues

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lisach

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I am trying to track down a problem with the power locks and the security system on a 1999 Yukon Denali 4x4. The issue is most prevalent when the temperatures are hot. It involves a combination of the front driver door, passenger door, and rear barn doors. It isn't always exactly the same combination. It doesn't matter whether it's initiated from the remote or a secondary lock. Can't believe it's the actuator on all 3 doors.

I read some similar threads with recommendation to change the master switch on the driver door. Trying to understand the process. Do all secondary lock switches (and/or remote key fob) send a signal 1st to the master lock which then sends a signal to all secondary locks and also the security system? Or does the secondary switch operate it's own lock 1st? Or is there a relay that intercepts the signal from the secondary lock and/or the remote key fob and distributes it? And if a relay could be involved, where is it?

Thanks in advance for your help.
 

exp500

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How old is your truck? And you don't have a manual? Take the time to download one for free or buy one.
First verify your theft light isn't flashing. A Tech 2 or similar would really help you here also. Link-https://www.autozone.com/znetrgs/repair_guide_content/en_us/images/0996b43f/80/24/b8/74/large/0996b43f8024b874.gif

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lisach

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How old is your truck? And you don't have a manual? Take the time to download one for free or buy one.
First verify your theft light isn't flashing. A Tech 2 or similar would really help you here also. Link-https://www.autozone.com/znetrgs/repair_guide_content/en_us/images/0996b43f/80/24/b8/74/large/0996b43f8024b874.gif

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Thank you for your reply. As the title says 1999. Yes I have a manual. But the manual doesn't give this kind of information. sometimes the light flashes and when I open the door (locks didn't fully engage), the alarm sounds. Other times I expected the alarm to go off when I could open the door, and it didn't. I've yet to be able to reliably reproduce the identical combination.

And thank you for the wiring diagram. I will endeavor to read, study and try to figure it out. Perhaps you could explain how to read this? Or perhaps you could point me to the instruction sheet for the diagram. Or maybe someone could answer my question with more end-user friendly information??

Again, I do appreciate any and all help.
 

exp500

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Factory manual or alldatadiy.com($60.00) are the only ones with troubleshooting guides and wiring diagrams that match scanners/computers. You could try Ebay for a factory download PDF probably $30.00 or so. Or search Like I did Duck Duck for ; wiring diagram 1999 Tahoe Yukon/ Factory Manual free download.
First thing to check is fuses after theft light not flashing. Good luck and keep replying to keep us updated.

Edit- rereading your post above, I believe you may have been mixing results of your searches. 1997 is a "safe" year for this GMT400 platform truck. Right in the middle of production. 1999 and 2000 Both style trucks were built. So stick with GMT 400 or OBS as some here call it. Lock sensor not in door latch assy on GMT400.
 
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exp500

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Any News yet? Your original description was vague for troubleshooting department. Seperate issues into key fob or door controls. Command/result. Both lock/unlock cycles from all key switches and lock buttons and status of theft light.
Could be just a failing FOB or unlubed door lock actuator. But everything is a guess without troubleshooting.
 

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