Shifting out of gear in cold weather

Have you tried fresh ATF-WS? It is a drain and fill, no flush, no filter.

 

This sounds like a problem with the electronic shift lever. I suggest taking video of the problem when it happens, and produce this as evidence to the dealer. This is not a major problem just requiring the lever in the dash to be changed "a simple job", but I agree you should not have to pay for this repair.
The shift mechanism is electronic and any gear selection from N to D to R to B is purely an electrical state within the transmission.
Mechanically nothing changes. In simple terms, reverse is just a change of direction of the electric motor, neutral is no electrical supply to the motor.

John (Britprius)

 

From what I've read, I agree with the shift lever diagnosis. I believe the rubber bezels/seals inside the shifter sufficiently harden at cold temperatures to cause unintended shifts.

 

Please let us know the final outcome of your problem. This is helpful to future posters with similar problems, and your input on anything Prius will always be welcome along with any questions you may have.
It would be helpful if you gave your location in your avatar.

John (Britprius)

 

It's also an easy repair if Toyota ends up stiffing you. I'd do it for $10 and the part. The only trick is learning to take the dash apart the first time.

You definitely shouldn't have to pay a cent though. I'd also like to know how it goes with Toyota. For reference, I've never experienced anything similar; it's definitely not a normal Prius problem. Sounds like the shifter is just slightly out of spec and heating/cooling expansion/contraction throws something off the tiniest bit.

 

I'm curious as to why he should expect to not have to pay for this repair, as his car is no longer under warranty. It would be great if he didn't have to pay of course, I'm just looking for the reasoning.
Unfortunately for me, I came from the world of BMW ownership where MANY things are expected to break, and very little was ever covered by dealers. Never again!

 

If the OP decides to DIY the repair, my thread here may be of interest. The shift lever is a known problem:
How to Replace 2G Gearshift Lever | PriusChat

 

This is definitely not normal, and the dealer needs to help you resolve it. This shouldn't happen at all, ever. If you can't reproduce it at the dealership, take a video of it happening.

Where I live, 25F isn't cold at all. The Prius is a car very well-suited to cold weather, and I've been through -25F weather already with no problems at all. I have no doubt that -40 will present no problems for it either.