Power Lock Doesn't Lock Rear Doors (Fronts = OK)

[Tenaya]

I have a 2004 Silverado Crew Cab Z71 LT with power locking/unlocking.

 

Recently, I noticed that although the REAR doors power UNLOCK properly (from the front door lock/unlock switches or the remote), they don't power LOCK. Since the FRONT doors power lock and unlock just fine, I think the central locking computer is not the problem. I took one of the doors apart and found only two pins in the connector on the actuator motor. I guess the central locking computer reverses the polarity of the signal it sends to the actuator depending on lock or unlock. That should mean that both actuators are good (they both make noise during unlocking and they actually unlock the doors) and the problem lies elsewhere, probably a loose connector somewhere between the computer and the rear doors.

 

Does anyone have the relevant electrical diagram that shows the central locking computer, the wiring, and, most importantly, where the computer and all the intervening connectors are?

 

Thanks in advance,

 

Tenaya

[scooby5121]

GM has a problem with the actuators.. I had mine done for free after warrranty was over.

They changed two of mine doing the same things yours are doing.

But I live in Ontario Canada.

 

Good Luck.. Scooby

[Stanley Z]

Mine did the same thing, they replaced them free of charge

[Tenaya]

Based on input from a variety of sources, I decided that my truck was suffering from a common GM problem, dead actuators; so I ordered replacements. This morning, when I installed the first one, it made no difference. The new actuator power unlocks the door (the actuator runs), but it won't power lock it (the actuator doesn't run). Further, it appears that the voltage on the line during a lock sequence is far below the voltage during an unlock sequence. The voltage is apparently too low to operate the actuator. I now suspect either the wiring from the central locking computer to the rear door lock actuators (bad connection?), or the central locking computer itself (does the truck have a separate computer/controller for the locking system, or is locking part of another system?).

 

Does anyone have the relevant electrical diagram(s) showing the central locking computer, the wiring, and, most importantly, where the computer and all the intervening connectors are? Again, I have a 2004 Silverado Z71 Crew Cab LT.

 

Thanks,

 

Tenaya

[elcamino]

There is a 5 sec delay on the rear doors of a CC. If any door is open or the tailgate is down, the doors will not lock. You can turn this feature on or off so its possible to turn it on inadvertently and if you push the lock button on the door or the tranmitter can toogle it on and off.

 

Could this be what you are experiencing?

 

If your vehicle is a Crew Cab, it may be equipped with

this feature. When locking the doors with the power lock

switch or the keyless entry transmitter and a door or the

liftgate is open, the delayed locking feature will delay

locking the doors and tailgate until five seconds after the

last door is closed. You will hear three chimes to signal

that the delayed locking feature is in use.

Edited May 14, 2012 by elcamino

[00Silverado4x4]

There is a 5 sec delay on the rear doors of a CC. If any door is open or the tailgate is down, the doors will not lock. You can turn this feature on or off so its possible to turn it on inadvertently and if you push the lock button on the door or the tranmitter can toogle it on and off.

 

Could this be what you are experiencing?

 

If your vehicle is a Crew Cab, it may be equipped with

this feature. When locking the doors with the power lock

switch or the keyless entry transmitter and a door or the

liftgate is open, the delayed locking feature will delay

locking the doors and tailgate until five seconds after the

last door is closed. You will hear three chimes to signal

that the delayed locking feature is in use.

 

 

This quote contradicts itself, is it talking a tailgate (truck) or a "liftgate" (SUV)? I personally use this feature in my truck and have always been able to lock my doors with the tailgate down, if not removed from the truck. I could see a "liftgate" having the wiring to show an open "door" and prevent doors locking, but a tailgate doesn't have the wiring from what I've seen in my truck. Just a question, not trying to peeve anyone.

[elcamino]

Thats a direct quote from the OP model year owners manual.

Edited May 14, 2012 by elcamino

[fileark]

If BOTH rear doors stop locking or unlocking or are intermittent it is probably the relays. They are in the drivers side door panel. If you pull them out you can notice that those two relays are for the rear doors only, the front doors will still lock and unlock. My symptoms were that the rear doors would lock and unlock intermittently, swapping around the relays didn't change anything because they were both flakey.

I didn't want to pay dealer cost or wait for shipping so I risked gently prying the relays open from the bottom and giving them a squirt of WD-40 on the contacts. Work perfectly now. BEST FIX EVER!!!

[gmtech4]

alldata .com

[SalX3]

On 7/5/2014 at 12:41 PM, fileark said:

If BOTH rear doors stop locking or unlocking or are intermittent it is probably the relays. They are in the drivers side door panel. If you pull them out you can notice that those two relays are for the rear doors only, the front doors will still lock and unlock. My symptoms were that the rear doors would lock and unlock intermittently, swapping around the relays didn't change anything because they were both flakey.

I didn't want to pay dealer cost or wait for shipping so I risked gently prying the relays open from the bottom and giving them a squirt of WD-40 on the contacts. Work perfectly now. BEST FIX EVER!!!

I’ve been experiencing this problem with my 2017 Silverado 2500hd. It started out with the locks working intermittently using the key fob and then about 6 months ago stopped responding altogether. Manually all work as they should. Do I need to replace the relays?