2006 Sonata doors will unlock, but not lock
 

Sorry if this has been covered. The car is at the mechanic, but he is having problems trying to figure what is wrong. I had thought it was possibly the door lock relays, but I no longer have the info I searched for the first time and don't have the time to search again.

Two things to check,
The door switch and the wiring where the front door moves at the hinge area, door pillar.

I think I need to clarify. The unlock, ONLY, works whether it is the key fob, button on drivers door, and key in door (which unlocks entire car also). Lock doesn't work. I have to manually lock the car. Hope this helps.

Each function has its own special wire/circuit and if interrupted for any reason it doesn't work.
The interruption could be coming from that function of the driver's door switch(Main) or the wiring to complete the circuit relaying the instructions.

This sounds like a faulty actuator
But, would have to test it by applying power directly to it to see if it works
If it fails to work properly then you have your culprit
If it doesn't then something else is wrong ... rusted links???

Had/have similar issues with my 2007 4-cyl Sonata--random non-responsive door locks when using the interior control or fob control. In my case it affects one door consistently (solution to this point has been to manually make sure it is locked before leaving the car), and others intermittently are affected. I spent a fair amount of time trying to diagnose the issue, but in general was thankful that only one caused a problem consistently and have just dealt with it.

HOWEVER, due to a recent broken part swap I have a hypothesis of why this issue cropped up--at least in my case. The interior door handle on the driver side of my car broke and I had to replace it completely after buying 1 week with some gorilla glue. Ordered the part from Amazon, and even though it was not OEM it was good enough for my budget and the lack of available parts at local junkyards. I've dealt with window regulator issues on almost all of my doors at this point, so I'm familiar with disassembling the interior door handle. When I installed the new driver interior handle with the amazon replacement part, I noticed the fit of plastic ends on the door lock/unlock cable sheaths into the interior handle unit was much more tight. They actually were hard to push into the slots, and snapped into place on the new handle unit. Every other time I've taken these things apart and reassembled, I have not noticed that although they fit snugly they were not as secure as they are in the new handle mount. Since I replaced the part (approximately 3 weeks ago), I have had zero issue with the driver door lock mechanism responding to interior or key fob controls, whereas the issues remain as before for the other (stock) interior handle/locks. [[i]see photo below in reference to the plastic ends of the cables that insert on the door handle mount/bracket].

https://cimg1.ibsrv.net/gimg/www.hyu...824318fb68.png

My hypothesis of the underlying issue in my car is that over time the fit of the cable sheath into their slots on the interior door handle loosen/fail. When the doors are told to lock/unlock using the electronic controls, the inner wire cable that runs from the actual closing mechanism to the interior door handle is extended or retracted within the outer sheath. So, my thinking is that if the ends of this sheath are not snapped into position, the overall tube (cable and outer sheath) may be able to bow/flex and undermine the movement necessary for the system to respond appropriately.

All this being said, I agree with the logic of other responses and recommend ruling those out as causes. I think I have pretty good evidence of what the problem was/is in my case, but this is based on my gut feeling and a major lack of motivation to keep chasing electrical gremlins that don't really affect the car's performance. I'll be much more sure after I order a replacement interior handle for the door that consistently has this issue and see if replacing it resolves the issue in that door. In the meantime, it might be worth ordering one/multiple of the cheapo replacement interior handles (I believe mine was ~$6, and there were sets for all 4 doors available for around $20) and swapping them to see if this fixes the issue.