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Rear barn doors power door lock not working

Tiny
BOULDERSKIES
  • MEMBER
  • 2003 GMC YUKON
  • V8
  • 4WD
  • AUTOMATIC
  • 117,000 MILES
The power door lock on the passenger side barn door is dead. It does work manually and all other locks function normally. I've replaced the actuator and checked fuses, but not the lock and unlock relays. Also there doesn't seem to be power getting to all the roof contacts which energize/de-energize the door lock. I know the location of the relays. Should I check them first? Also, how do I test the roof contacts?

Thank you, Scott
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Thursday, January 24th, 2019 AT 8:44 AM

12 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,490 POSTS
Hello,

The lock and unlock relays are in the inside fuse panel. here is a guide to help you test them and the relay location with the wiring diagrams so you can see how the system works:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

This guide will help you check the connections:

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.
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Friday, January 25th, 2019 AT 12:00 PM
Tiny
BOULDERSKIES
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Thank you for your reply. I believe a key factor in diagnosing this problem is the fact that the two rear power door locks work fine; just the cargo door lock does not. Fuses and relays appear to be functioning fine (or the two other door locks would not be). Relays click as normal. I would like to concentrate on the rear cargo door contact plates next (pictures attached-pin shown that is activated by key fob lock press). How do I test them to ensure good connectivity? Which wiring diagram shows which wires go where?
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Saturday, January 26th, 2019 AT 5:40 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,490 POSTS
Yep, that plate doesn't look too good. You will need to close the doors and then remove the panels to access the wiring on either side to test through the contact plate. Make sure you have power at each of the fuses in the system check out the wiring diagrams to show you the fuse number. Please let us know what you find.
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Saturday, January 26th, 2019 AT 11:19 AM
Tiny
BOULDERSKIES
  • MEMBER
  • 20 POSTS
Sometime ago I had scraped each of the contacts on the plate thinking that would make for a better conductive path. That's why they look that way. But that really didn't help.

I just spent some time tracing the wires (at the roof-top pins, the contact plate and the i/p panel on passenger side dash) and referring to the wiring diagrams. I think I am principally interested in the grey and tan wires. So I guess what I need to know is specifically how to test wires that enter a connector with a 12 volt test light. Do I stick the probe down into the wire in question? If so, where do I connect the alligator clip? Or do I need to connect the clip?

It feels to me as if the lock and unlock circuit are not getting energized.

Ken, seriously-a note of thanks for your responsiveness and help.

Scott
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Saturday, January 26th, 2019 AT 12:39 PM
Tiny
BOULDERSKIES
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Also, can you provide the path to the wiring diagrams above? Thanks, Scott
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Sunday, January 27th, 2019 AT 5:22 AM
Tiny
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Finally-from the wiring diagram, it appears the tan wire is the unlock circuit. So if I connect the alligator clip of a test light to ground, the probe to the tan's female connector in the roof harness and push the Unlock button on the key fob, shouldn't the test light illuminate?
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Monday, January 28th, 2019 AT 4:10 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,490 POSTS
The tan wire should have power when you press the switch. Does it?
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Monday, January 28th, 2019 AT 12:38 PM
Tiny
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Sorry for the delay. I have confirmed power on tan and& grey wires to back and front of connector for roof-side pin-connector on passenger side of roof for cargo door. However, it seems no power is getting to the pins on the other side of pin connector. I have a new pin connector for roof and will advise once installed.
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Sunday, February 3rd, 2019 AT 4:44 AM
Tiny
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The new roof connector is installed. The rear cargo door power lock is now working! Ken, thank you again.
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Sunday, February 3rd, 2019 AT 7:37 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Good to hear, please use 2CarPros anytime we are here to help.
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Sunday, February 3rd, 2019 AT 12:23 PM
Tiny
TODY RORLS
  • MEMBER
  • 1 POST
  • 2007 GMC YUKON
  • 4WD
  • AUTOMATIC
  • 130,000 MILES
The rear doors will lock with the automatic locks but will not unlock. Help.
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Sunday, February 3rd, 2019 AT 12:30 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check the fuse and relay in the pic then if those are ok have a mechanic scan for codes if no door lock codes have him scan for sir codes as there is a tsb from GM that some sir codes will not let the rear door unlock.
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Sunday, February 3rd, 2019 AT 12:30 PM (Merged)

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