2001 Hyundai SantaFe Left Rear Intermittent Unlock

So, I'll start off with saying that I replaced the lock motor with a used part and it's working for now. The main point about this post is that the system seems rather unusual to me. I can make a few guesses at its operation but I'm wondering if anyone has more experience/information.

It's a 2001 Hyundai Santa Fe 2.7L AWD Base model. The left rear power lock would always work. Unlock would usually work if the locks hadn't been cycled in a while. But if you locked the vehicle then quickly unlocked it it would almost never unlock. One thing I've noticed with this vehicle is when you hit Lock the actuators would SLAM into the lock position yet the Unlock function was much softer. I'm not sure if this is by design for security? I've never really paid much attention to it on other vehicles. Maybe the logic is it's better to have a door fail to unlock then fail to lock and leave your vehicle vulnerable?

The circuit is setup so that it goes from the lock relay, through all the door locks then back through the unlock relay. Terminal 87a of both relays is ground and 87 is power. So when the system wants to perform a lock/unlock function it just energizes the corresponding relay to provide power and the other relay provides ground via its 87a.

That's all fine and good. The part that has me unsure is it has an unusual feedback system to let the module know if the actuator really did switch state.








So I'm guessing the design of it is when the actuators are in the locked state it'll pass ground up to the ETACS module. Then when you unlock it it acts like a relay and by electromagnetism moves the contact switch to the open state and removing ground from the feedback wire. I'm fine with that but one of the things that confuses me is the feedback wire for both rear door locks and the liftgate lock all splice together then go to the ETACS module. Both front doors have their own signal to the module. That strikes me as odd. If one of them sticks then that wire will always have ground I guess it probably has a timer where it will energize the actuators for a certain amount of time unless it detects all successfully operated? Likewise, why bother having separate feedback signals on each front door? The system is not capable of energizing a specific actuator. It can only do all at once. I'm not sure if any of these early 1st gen Santa Fes had any kind of factory security system...

It's my vehicle so I had time. I pulled out the Verus and did some captures to see if I could spot much between the before/after.

My setup was:

Yellow: Voltage trace on Blu/Org wire coming from unlock relay
Green: Voltage trace on Org wire coming from lock relay
Blue: 20A clamp on Blu/Org wire. Oriented so that positive current indicates lock function and negative for unlock
Red: Voltage trace on Blu feedback wire


Lock with old actuator:




Unlock with old actuator:





Lock with used replacement actuator:




Unlock with used replacement actuator:




I know I didn't leave enough room to show the peak of the current scale but peak current was pretty well the same for before/after.

If you have Snapon's ShopStream Connect and want the .VSM files then here they are. I had to put them in a .ZIP because the forum wouldn't let me upload the .VSM by itself.


Bad actuator:




Good used replacement actuator:






Now, if you look at the wafeform for the bad actuator you'll notice a few cycles where there was no difference in the current pattern. I'm not sure why that is. It seemed to mainly happen when I tried repeating an operation. Like hitting lock after it already locked. Maybe this actuator has an internal mechanism that opens the circuit when it tries to perform a function that it's already in..? Unfortunately I didn't try repeating a state on the replacement one so I don't have anything to compare that to. Otherwise it's possible that maybe internally it was shorted to the Brn/Org wire and getting ground from there? Even when there was no current pattern the actuator was being energized and was trying to move.

So ya, that only real difference I noticed was in the Blu feedback wire. It was around 3V instead of 0.5V. Maybe that's all electromagnetic induction from the motor and indicates the strength difference of the two motors? Also I noticed that pattern had quite a slope to it on the old actuator where the replacement one was much more of a square wave.

So the other thing that seems odd is the feedback wire on the lock function went to -3V. That's -3V in reference to chassis ground. So I guess it would have to be electromagnetic induction. Maybe the first part of that waveform on the lock function is open circuit in the beginning, then -3V from induction while the motor is spinning then stops at ground when the actuator moves fully.

Also I don't know why the current pattern on the unlock cycle had all the hash in it yet the lock operation was clean. Both actuators showed that characteristic on every cycle. Maybe that's why the actuators hit so hard on the lock yet were softer on the lock operation? When you hit lock the actuator moves a tab away from a lever attached to the latch mechanism. Then when you pull the handle that tab misses the latch lever and doesn't unlock the door. When you hit unlock it brings that tab back over the latch lever. Maybe they just cycle the unlock in case things are out of alignment and the tab hits the latch lever and jams up..? That could help prevent burning up the motor.

It all seems kinda goofy. I'm just wondering if anyone has more insight on this kinda setup. I'm not sure if going this far will be of any real use as there's no way you'll ever find documentation on what's supposed to be on that feedback wire. I just like trying to learn as much as I can when I come across something I'm not familiar with.

Cheers!

I'm going to look at this more in-depth tonight. I'm so curious as to why the unlock operation has so much current 'ringing' yet the voltage graph doesn't show it.

Any thoughts on that? Any discoveries?

I would think the new actuator would have helped with this.

I'm really not sure. I was totally expecting to have more of a difference between the two actuators. The other actuator was from a salvage yard but the pattern was pretty well the exact same... It might even be a normal characteristic for these actuators..? When I feel more energetic I might pull back the doorjam boot on the other side and grab a current reading off that side. See if it has the same pattern.

Well, we know that ringing is caused by changing resistance; unless voltage is changing to it via PWM. So, for some reason, I'm guessing we are encountering changing resistance.

Clearly, there is a coil in the actuator which causes ringing, but this just looks so different than when being locked. It also just looks like it is working so hard to move the unlocking mechanism.

I guess I would check physical issues and powers/grounds to that actuator compared to the others.

Yes. I know. Tearing apart a door isn't something many people love doing. I dislike interior stuff.

But, this might be the root to your problem; that is to say this weird ringing.

Best of luck. Your persistence will pay off.

That's just the thing though. I replaced the actuator. The top capture is my old actuator that wouldn't unlock most of the time. The bottom capture is after I replaced it with a used actuator. That one works 100% and has the same current pattern. So either it's a physical problem or maybe it's just an electromagnetic effect that only shows up when the current flows in that direction. It could be totally normal. After all, EVERY door lock on the car hits really hard and loud when locked but they're all soft when you hit the unlock.