Door lock actuator - rear lift gate

I have an apparent problem with a door lock actuator, and hope someone can provide a bit of background on how they operate.

The patient is a 1999 Toyota Sienna LE, and the door is the rear lift gate, but my question is more about how these electric switches work.

The problem I have is that the actuator will lock the latch every time, but has now entirely stopped UN-locking it.

Is that because there are two separate solenoids within the actuator, one for each direction, and one has failed?

I’ve studied the mechanism and have a pretty good idea of how it works. I can’t see anything physically broken, and I understand what has to happen to unlock. With that knowledge, I can unlock it manually with a small hook tool. If the new part were half the price it really is, or less, I’d just buy a new one. But it’s more than twice what I want to pay.

I’ll try scavenging at recycling yards in the next few days, but meanwhile, can anyone provide any insight into this?


I do not have a wiring schematic, but I might guess there are 2 wires going to the actuator. You should have voltage somewhere when one hits the unlock button. If there is no voltage check the fuses, or look at the wiring in the bundle to the liftgate for a broken wire.

The device is an actuator, not a solenoid. Basically a little reversible electric motor. I’d power the actuator manually to see it it works both ways. I’d also probe the connector and hit the lock and unlock buttons to see if you are getting power and ground and if it switches polarity when switching from lock to unlock.

Depends on how many wires go into the actuator to be honest… @Mustangman is correct…try that test.

Its probably a problem internal to the actuator where it isnt making connections internally when its in the locked position, so it cannot initiate the unlock movement…

Thanks guys.

What I was puzzling on is whether the actuator is performing one action, and not the other, and how that can be. That’s why I had previously wondered if there were two separate solenoids, one for lock and another for unlock. If I correctly understand your replies, it’s just one device, a motor not a solenoid, which accomplishes actions in two directions, except that in this case, the unlock action is impeded by something.

But I have just made an important discovery:

For the moment I don’t have an assistant to operate the driver door lock switch while I watch the problem area. But since the interior panel has been removed, while standing at the driver door, I can clearly see the rod which connects the key lock to the latch mechanism as I press the lock switch. That rod, and the lock, are moving in both directions, but apparently not far enough to unlock, confirming that there is indeed motion in both directions from the actuator. That takes me back to wondering about the latch mechanism, which is two plates with slots and a pin that has to move upward to align the plates properly. I’ve been manually moving that pin in a way that allowed the latch to move to release. So maybe there’s some simple impediment to the full range of motion?

I’ll get back to that later today.

Yep, got that, thanks. I was editing my reply as you were clarifying.

Applying a little lube on the friction points that affect the lock/unlock linkages makes sense at this point, maybe you can free it up that way.

The actuator is probably a type of servo motor. It might move one direction with +/- voltage input, and the other with -/+ voltage input. So measuring that might provide a clue. I expect you’ve got one of three problems

  1. The switch that controls it is faulty
  2. The actuator is faulty, in which case getting a replacement at a junk yard is a good idea.
  3. There’s some mechanical binding somewhere in the works.

I started out thinking it was something related to the two plates with the slots, and the black pin that penetrates both, rather than the actuator. I am back to believing that, and not a problem with the actuator.

There does seem to be interference with the latch parts causing the problem, and it looks like the design shouldn’t work at all because of that interference. But that’s the way it was built, so that can’t be it. There must be something I’m not recognizing.

So I used a dremel to very slightly modify the part of the plate which seems to cause the interference, and that was unsuccessful. Lubing didn’t change anything either, so tomorrow, I’ll prowl a few junkyards to see if there’s something different about another of the same, and why. Pick 'n Pull will charge me $17 if I can find one that works differently. Otherwise, I’m stumped.

BTW George, the switch operates all the other door locks, and as I wrote earlier, I can see the rod between the lock and the latch is moving in both directions. Maybe the motor is not moving the pieces with proper force, but I’m not buying that. I have to think that the issue is with the latch parts and maybe there’s something worn out that isn’t detectable.

You know… those door lock latches dont last forever either. Maybe the lock unlock arm pivot point is all hogged out and sloppy… Latches fail all the time.

Yeah, thanks Blackbird, I think this very well could be just what you said.

I’ve had the latch out of the gate and operated it in my hand dozens of times today, and can’t perceive what is causing a problem that I can clearly see. Usually I’m good at understanding how this kind of thing should work. So it’s probably just as you say, accumulated wear on a mechanical part on a 20 year old machine. Just like my body looks more or less the same as it has for decades, but some parts are not working like they used to! :wink:

Oftentimes you will see that a door latch needs more movement in one direction than it needed prior to accomplish a task because of wear. Your latch may be easier to lock needing less actuator stroke than to unlock which now needs extra actuator stroke due to wear… Or whichever way if I juxtaposed the failure mode. This crap happens all the time.

Nothing lasts forever

Maybe you could move an actuator from another door to the rear one as a test, assuming they all use the same actuator part number of course.

BTW: Is this a problem you need to solve? I opened my VW Rabbit’s lift gate lock with a key for many years, never failed once. If you can open the lift gate manually with a key the best option may be to just do it that way from now on.

George, since the actuator connects to a unique latch mechanism, I would doubt that the swap you propose would be plausible. Anyway, I got one at Pick n Pull this afternoon, but too late now to try it.

Isn’t going to Pick N Pull fun? I always enjoy going there, even when I don’t find anything I need.

What part do you like best? Is it the dismal neighborhoods where the places are located, or dangerous looking people in the parking lot eyeing your vehicle, or trekking to the ends of the earth to find a match for your car - only to find that somebody else had already taken the part you need, or the chaos in the “office” trying to sign in or pay on the way out?

I had all of that in just 30 minutes today! While wandering around, I offered a friendly and carefully neutral greeting to somebody toiling in front of a car. He responded using words I’d heard before except that the order in which he said those words were arranged in a sequence that made absolutely no sense. Luckily, by then, I was far enough away that my failure to continue the conversation was not a problem.

My gf tells me not the take either of my cars there to the parking lot at P & P b/c folks will think they are so old they must be for taking parts from … lol … so far nobody has taken any though. If you’d ever catch me working under the sink fixing plumbing I bet you’d hear even worse words, something about plumbing that brings out the extra words in my vocabulary … lol .

Just a few years ago you asked what goes on there, not you visit them frequently?

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LOL I could not help but smile and have a pretty good laugh after reading @WesternRoadtripper1 description of going to a Pick N Pull type of yard.

Dont get me wrong… I’m not from the other side of the tracks, not by a very long shot, but I know where the tracks are and I cross them often. I also live just outside of Philly and all of her car yards. Let me tell you brothers n sisters, if you can visit any and all of Phillys yards any other yard anywhere else (maybe besides Ghana or Bangladesh) are going to seem like a country picnic party. I could write endless stories about the topic to be honest, some funny, some confusing and some downright nutty and or scary.

Alas, I chose this sand box to play in and honestly I enjoy it… all of it. But I can definitely see why Western might have felt a bit out of place, I need to remind myself that the situations I get into often cannot be considered “normal”. So… I do get it. I’m laughing as I type this thinking about this topic.

Perhaps I need to write a book.

The replacement latch and actuator assembly is installed…and NO improvement. So that’s not the problem, but it was worth the effort.

I guess that means it’s an electrical issue after all. For that, I have a message in to my mechanic. This may be out of my league.