Don't know about the diesel but you might try pulling the PWRTRN fuse and it resets the auto trans. Might work unless the non US models are set up differently. Good luck.

 

Hello,
So here is what i have figured out in past days.
At the time the problem occurred there was heavy rain and a lot of water on the roads.
A day after i decided to look again and tried to found the problem, but know what, everything worked normal. Jeeeeiii!!
So it seems that something was wet and after drying it is ok. But what?
A car was doing great few days until i washed it. After that again no reverse!
Maybe some suggestions what electronic part could produce this problem?

 

I have the same problem on my 2008 Sorento 3.3 and I wondered if you found the connector which may have gotten wet. We have had monsoons lately so wondered which connector is vulnerable to shorts due to water.

 

Crawl under the beast and look for any boots that may have come loose allowing water to enter an electrical component.

 

Depends to some extent how you washed it. Jet wash in the engine bay is a recipe for disaster! [water can get into fuse boxes from below]. On this age of vehicle any exposed harness connector is a candidate for corrosion and/or damage. Water leaking at top of windscreen or sunroof (blocked drains) can find it's way down into the interior fuse box and/or relays.

 

Curious, given this is an old thread I found, surely more people had the same issue of erratic reverse failures. I just experienced in on my 2008 3.3 Sorento with only 96K and I changed the trans fluid at 38K and when I changed again it looked super clean, no burn odor and used KIA trans fluid and same issue. I disconnected battery and when a reconnected after 10 minutes it went right into reverse, no slipping, but then it went back to slipping after about 20 minute drive. All forward gears work perfectly with no sign of any issues. I pulled the TCU to check connections and ground and all looked clean and new. After all these years surely, someone must have experienced the same, so wondered what else to look for. Thanks in advance for any input.