'07 Yukon XL Denali rear door unlock

[BSarteSr]

I am back to working on the rear doors unlocking (or better said that they don't) on my '07 Yukon XL Denali.

When I press the unlock button the 2 rear doors do not unlock, posted about this already and still working on it!

When I press the unlock button (either on the door button or on the remote) I can hear a relay clicking. So today I took the dash apart enough to see the relay (see attached pictures). It is on the back side of the fuse panel. Took it out and on the top of it has 12088575 and looks like it is 25 amp. On the side of it is 6182. It is 2 prong, tested it and has good continuity.

I also tested the fuse (15 amp) in the fuse block that says "door unlock" and that is good.

I am again at a loss as to why my PITA back doors will not unlock (but they will lock just fine).

Any input PLEASE!

 

[Airman68]

My philosiphy is most problems are not complicated so look for the simple solution firast. First thing I would ask is if you checked to see if the unlock signal was getting to the back door. Could be a wiring issue or the unlock hardware in the door is malfuntioning. If your getting the unlock voltage to the unlock mechanism, then it's a hardware issue.

 

[dustyb]

I've had the same issue for quite a few years as well. Both rear doors would lock, but only unlock intermittently (usually after pressing unlock multiple times). It seemed to be worse in the winter. They've finally completely stopped unlocking, even with excessive unlock button pressing. You can hear a relay clicking very loudly when pressing the unlock button.

I tried replacing an actuator a while ago, but that didn't work. I know actuators are a common problem on these, but it's hard to imagine that both doors acting exactly the same way would be the actuators in each individual door. I've checked the wiring in the B pillars and those seem fine. Fuses are all good. I'm not sure how to test if the proper unlock signal is getting to the lock actuators.

I'm debating whether or not I should purchase a new instrument cluster fuse/junction box where the relay is located.

 

[BSarteSr]

I've had the same issue for quite a few years as well. Both rear doors would lock, but only unlock intermittently (usually after pressing unlock multiple times). It seemed to be worse in the winter. They've finally completely stopped unlocking, even with excessive unlock button pressing. You can hear a relay clicking very loudly when pressing the unlock button.

I tried replacing an actuator a while ago, but that didn't work. I know actuators are a common problem on these, but it's hard to imagine that both doors acting exactly the same way would be the actuators in each individual door. I've checked the wiring in the B pillars and those seem fine. Fuses are all good. I'm not sure how to test if the proper unlock signal is getting to the lock actuators.

I'm debating whether or not I should purchase a new instrument cluster fuse/junction box where the relay is located.

Yes, I have done all the same as you but these PITA rear door locks will not UNLOCK!

It just boggles my brain as to why the fronts work fine and the rears will lock but not unlock. I doubt that it is a wiring problem since it is both back doors.

Any GM Engineer's in the crowd?

 

[mikez71]

Sure it's probably your VASS module!

Sorry just kidding I have no idea what/where the VASS is.. but it's in the wiring diagrams that nobody can understand! And it does connect to your doorlocks..

See you have the Lock/Unlock relay and the Unlock relay.. makes perfect sense right?
Looks like tan and grey wires to the motor.. something must flip polarity or something something..
headhurts.. naptime..

About the relay you found..it maybe your signal flasher.
Keep us posted, would like to have an idea how the doorlocks work!

 

[B-train]

Going towards the simple route, is the child lock engaged for some reason? Ther ususis a little rocker switch I think on the door panel? Maybe I'm wrong, but thought there was a manual lockout

 

[B-train]

Dang, sorry for the fat fingers..........again

 

[Fless]

That's not a relay, it's a circuit breaker. Relays need at least 4 contact points, and sometimes have more.

 

[mikez71]

That's not a relay, it's a circuit breaker. Relays need at least 4 contact points, and sometimes have more.

Ah.. makes sense why it has 25 on there.. Thank you Fless!

That circuit breaker is for the left door or doors.

Both rear doors are connected to the same circuit, Fuses for unlck1 and lck1..

lck2 and unlck2 fuse is for the endgate? Seperate relay for liftgate, so I'm not sure what endgate is, seperate liftgate lock maybe, but it is also connected to your doorlock relays. So endgate should be locking but not unlocking for you as well.

Looks like both lock and unlock relays are normally grounded, and when you hit the switch, one connects power to lock, or the other connects power to unlock. They utilize the ground of the opposite relay.

looks like relays are on built in the pcb in the instrument fuse panel. .

 

[BSarteSr]

Going towards the simple route, is the child lock engaged for some reason? Ther ususis a little rocker switch I think on the door panel? Maybe I'm wrong, but thought there was a manual lockout

Checked that, turned it on then off again.

 

[BSarteSr]

Sure it's probably your VASS module!

Sorry just kidding I have no idea what/where the VASS is.. but it's in the wiring diagrams that nobody can understand! And it does connect to your doorlocks..
View attachment 398365
See you have the Lock/Unlock relay and the Unlock relay.. makes perfect sense right?
Looks like tan and grey wires to the motor.. something must flip polarity or something something..
headhurts.. naptime..

About the relay you found..it maybe your signal flasher.
Keep us posted, would like to have an idea how the doorlocks work!

Any chance you have this for the 4 door vehicles?

 

[mikez71]

Hi BSarte, that diagram is for the 4 door vehicles. The diagram is for the rear doors.

I am guessing VASS is just an acronym for the system like 'stabilitrac' which is integrated through the ecm, brake module, steering/yaw/wheel sensors etc.

Main thing is the locks use the same wiring for lock and unlock and for both doors. And if the relay can be heard clicking, then the relay is getting the signal from the BCM.. so it seems to me like the relay switch contact maybe bad.

Just think, your locks could have lasted twice as long without the auto-doorlocks!

I wonder if its possible for the lock motor to fail partially shorted.. not enough to blow a fuse, but put extra current through the relay and arc the switch contact. Speculation, but searching the web, there can be partial motor shorts.

So if one of my doorlocks quit working (and it should quit working for both lock AND unlock) I am going to try and not use the power doorlocks until the bad one is replaced.. wouldn't matter if motor is not shorted, but just in case.

I am curious what the PCB looks like in the fuse panel.. hopefully the relays can be replaced with some soldering

 

[dustyb]

Hi BSarte, that diagram is for the 4 door vehicles. The diagram is for the rear doors.

I am guessing VASS is just an acronym for the system like 'stabilitrac' which is integrated through the ecm, brake module, steering/yaw/wheel sensors etc.

Main thing is the locks use the same wiring for lock and unlock and for both doors. And if the relay can be heard clicking, then the relay is getting the signal from the BCM.. so it seems to me like the relay switch contact maybe bad.

Just think, your locks could have lasted twice as long without the auto-doorlocks!

I wonder if its possible for the lock motor to fail partially shorted.. not enough to blow a fuse, but put extra current through the relay and arc the switch contact. Speculation, but searching the web, there can be partial motor shorts.

So if one of my doorlocks quit working (and it should quit working for both lock AND unlock) I am going to try and not use the power doorlocks until the bad one is replaced.. wouldn't matter if motor is not shorted, but just in case.

I am curious what the PCB looks like in the fuse panel.. hopefully the relays can be replaced with some soldering

I've kinda of speculated that it was the instrument block with the built-in relays. It's $80 from gmpartsdirect.

I've also speculated that one door actuator is bad, so it's drawing too much current causing both to fail. I believe unlocking takes a little more effort from the actuator, so that's why that fails to engage. 100% just guessing here.

I think I'm going to try unplugging both door lock actuators, plugging in new ones(without going through the effort of installing them) and see if that that does anything. If it doesn't, I'm going to try replacing the instrument panel fuse/junction block.

I'll post back with my results as soon as I get the stuff and test it out.

 

[Mean_Green]

Not familiar with this year vehicle, but most lock actuators are simple solenoids or DC motors. 12V to one wire locks, 12V to the other wire (reverse polarity) unlocks. (Pulls solenoid vs. pushes solenoid if you will)

Not digging into the wiring diagram, is there a common scheme for the two rear passenger doors that is somehow different from the two front doors? Is there a common point or component?

Have you had the doors apart enough to get to the connectors? If so, can you put a meter on them and see if the voltage is reversing polarity? Can you apply 12V direct to the actuators without any of the vehicle buttons or controls involved? That will test them to see if they're good or bad. Would/could both fail? Well, on my '95 Taurus all four power window motors failed within about a week of each other. I had to replace them all.

Now, all of that assumes this system uses simple power principles and is not computer controlled somehow on you newer than mine vehicle.