I live in arizona, my door locks including the rear hatch work fine in the winter but when the hot weather arrives they all stop working you can see the push pull lock on the doors move a little like they are trying but wont lock or unlock, I've been getting by by using them manually but my tailgate lock with the key doesnt work so I'm stuck not being able to lock(or unlock) the tailgate. my runner has 300k so its well worn. debating putting on a lock hasp on tail gate so I can secure it this summer, but I sure would like to figure out the problem,note: this problem has gotten worse over the last several years

The lock actuator motors failing as they get old is pretty well documented, and the behavior is much more evident in the heat. You can check out a thread on replacing the actuator motors here, or a good video on replacing the actuator motors here.

Just as Skulking said, your door lock actuator motors are old and need replacing. My locks also wouldn’t work in hot weather, but worked fine when cold. I purchased new motors for around $20 for the set of four on eBay, spent a few hours replacing them, and now all work great!

On a side note, and note to highjack this thread, but has anyone replaced their rear hatch actuator motor? It sometimes gives me trouble during hot weather, and I haven’t been able to find any info regarding the replacement of just that motor. I’m curious if the actuator uses the same motor that the doors use, or if it requires a different motor? Or maybe a whole actuator replacement?

You will be needing this.

Tim’s video is spot on and I used his guide when my drivers door failed. Not too hard to do and very cheap.

Don’t know about the rear hatch. Would be interested to learn if it’s the same process and motor.

Replacing my door lock actuators with new Toyota actuators fixed my door lock problems in the heat. I planned on replacing just the motor but couldn't get the 2 halves of the actuator apart. I found out later that it has to be cut open & not pried open.

It's probably a coincidence but after replacing all 4 door lock actuators, summer 2019, I haven't experienced any rear hatch lock problems. My initial intent was to also address the rear hatch at the same time but I wasn't able to get confirmation if it operated the same way, regarding the actuator, but so far so good & my rear hatch was definitely problematic before replacing the actuator in all 4 doors.

One thing that I had different from your situation was I could still manually open my rear hatch with the key. It was just the power function that didn't work when exposed to the sun or hot out.

so I learned some more my key lock assy on the tailgate wouldnt turn after a PITA getting too it I removed it and it would not turn with the key, I was hoping to at least save the manual locking availability, so I bought a new key lock assy (came with keys and electrical plug from of all places United Arab Emirates on ebay. a genuine toyota part for $60 shipped, instead of $150 from the local dealer , go figure half way around the world in 5 days for almost a third of the price. unfortunately the cylinder is glued into the plastic facia and I have no idea how I'm gonna get it out without breaking the plastic which of course is god knows how old. the glue looks to be something close to JB weld (not rock hard but still to hard to pry off of the 20 year old plastic any one ever do this with out having to buy a new facia?????

I'm pretty sure that when I pulled my trim to install a backup camera the lock assembly was just held in by two Phillips head screws. If it's glued in, you probably have the previous owner to thank for that and should start looking for replacement trim.

another FYI I got out my dremel and ground away at the ?JB WELD? when it got thin enough I started rocking the lock until it eventually broke out of the trim piece. it seemed to be very securely anchored in there so I saw no reason to go looking for a new for a new tailgate trim face especially since they are expensive or used ones are old like mine. JB WELD is setting up now so I'll start reinstalling in the morning. so a few hundred dollar (parts) turned into $60 plus a tube of JB weld and I can always find more uses for that. next project will be replacing the door lock motors. My runner has 295K on it and all the big parts are humming along like new. its all the little parts that are wearing out