Scary! Parked car shifted into drive by itself

I'm curious where you see that. I've been eleven years on PriusChat and haven't heard of it.

The design of the shift control (and the interlock with the brake switch) seems to make it awfully unlikely.

 

Take it to the dealer - they'll be able to check the Event Data Recorder and the Vehicle Data Recorder which will have recorded anything untoward.

 

That‘s a good suggestion, not only because a Vehicle Control History event might have been recorded (though EDR data are unlikely to have been saved, since there wasn’t a collision), but also because it shows diligence in trying to have any problems fixed, in case anything similar happens again.

I’m also inclined to agree with @ChapmanF: from the descriptions in the New Car Features and Repair Manual books (more info), it’s clear that Toyota recognized the safety importance of the Electronic Shift Lever System and paid a lot of attention to preventing inadvertent operation.

When you pressed the P switch, did you check for the green P indication on the combination meter?

If the car was still moving when you pressed the P switch, for example, it would have shifted to neutral (N) instead (as designed) and then might have remained stopped on its own for a while. If this is what happened, I’d imagine it would appear in the Vehicle Control History as events X0500, Shift P Operation During Running, or X0515, Shift P Operation Before Vehicle Stop.

 

Most likely you pressed park and it didn't go to park, it went to neutral for one of many valid reasons. But relatively flat terrain made it appear like all was well and the spidey senses said you were parked even though just free-rolling. Then something, wind, rock moved, pigeon fart, whatever, and you started rolling. It is highly unlikely bordering on impossible the car can do this. There are so many interleaved safety systems and overrides.

 

I know on the Gen 2, the plate behind the shifter is plastic so it will warp and when you shift, it can remain in drive. Did you kick the parking brake on too or no?

 

Are you also absolutely sure it went into D?

The reason I ask is that I've experienced this too several times, maybe...

Even in P, the front wheels have a bit of slack. Enough to allow the car to move maybe half an inch in either direction. A quirk of the planetary gear set is that if you press P while the ICE is on, and it's charging the HV battery, then at some point later the computer will want to stop charging and/or switch off the ICE. It does this by first disengaging the MG (to stop charging) for a couple of seconds before it switches off the ICE. During those 2 seconds, the kinetic energy stored in the MG has to go somewhere. It can't back feed into the ICE easily, the battery is no longer accepting charge (the charging system effectively disconnects it to protect it), so the first (easiest) place it can go is into the wheels. Being in P means there's only that half an inch of play before it's physically stopped (and the energy turns into heat), but for those 2 seconds the car will try and move forward gently. It's enough to feel a small but gentle and controlled lurch (as if someone was doing a hill-start in a car with a manual gearbox) and also make the foot-parking brakes holding the rear wheels squeak if they're not on hard. But that's all that happens - i.e. the car will move only as much as the slack allowed in P mode, and it does it slowly.

 

Another possibility, though he didn't mention the ICE kicking in, is that often the car will lurch when the ICE fires up after resting in Park for awhile, either to provide heat or to charge the traction battery. This would be enough to startle someone who is not expecting it into thinking the car is beginning to roll. I've been there...

 

I would take it to dealer and get it on record and get a receipt so that if it happens again you will be covered.
Maybe operator error, maybe not?

 

Exactly. This is in fact the same thing as I described, but I'm reverse. Scared the hell out of my wife once while I left her and the kids in the car briefly to grab something from the house.

 

I noticed my 2016 doesn't seem to have a violent movement when the ICE starts like my 2008 had.

 

Bad 12 volt

 

I appreciate this doesn't answer your question, but how about a paradigm shift: whenever you're parked, turn the car completely off, and set the parking brake. Turning it off will also, for sure, put it in Park.

There's a anti-idling bylaw in Vancouver, pretty much never enforced. I think law enforcement vehicles are the worst offenders, closely followed by cabs, and pretty much anyone in a diesel truck, lol.

Idling regulations | City of Vancouver

 

I wonder if that idling law is aimed at curtailing emissions from non-hybrids. Reading through it, there is no mention of what type of vehicle is exempt.

 

Oh no, not another haunted Prius

My guess is that one of two things happened, either you pressed the park button without your foot on the foot brake, so it went into neutral, or you pressed the park button too lightly and it didn't register.
What you need to do now is see if you can replicate the event by doing the above.

 

Maybe no exemption needed? Generally when I'm camping or doing hunkering tests, as long as the heat or A/C aren't set to extremes, the engine cycles in bursts that don't seem to reach three consecutive minutes.

 

Keywords: Button and Shift.

Sorry, but this almost has to be a cockpit error....or in this case....error(S).
If you're going to park your car with the engine running, you really should set the parking brake and make SURE that the car really is in Park.

Since your car is closing in on three years old, if you REALLY want to pursue this then MAKE the dealership note in the vehicle history that there was an un-commanded shift into drive while parked and that you believe that the whatever they call that goofy little joystick thing on your dash is a possible contributor due to wear.
Tell them that you intend to pop a flare over the NTSB and remind them that only two mysterious incidents with Boeing's relatively new 737-Max is trashing Boeing's stock right now.
They won't care of course...because they SELL cars, they don't build them.
BUT!! in the very unlikely event that there is a real problem with your car that isn't sitting in the left-hand seat, you will have documented at least one spontaneous drive mode shift.
If you wind up being right, this documentation might be beneficial.

Me?
I'd want to make sure that the shifter really is bad before I'd let somebody tinker with it, but it's YOUR car.

Remember.....
It really isn't a "shift lever."
It's a slightly beefed up joystick with springs and electrical buttons, and people do the most amazing things with them including replacing them with aftermarket junk.
But hey....even real shift levers break.
This is why they developed something I like to call a Parking Brake, which is not to be confused with a Hand brake or an Emergency brake.

Toyota might even call theirs a parking brake, and since owner's manuals are written at the behest of lawyers, there's probably a blurb in their manual about using this device while......parked.

State laws are even simpler.
If your car hits another car it's almost always going to be all the way YOUR fault....even outside Vancouver where they allow private citizens to idle their cars.

Good Luck!

 

I think you can leave your engine running here with a pet in the car

 

Why would the condition of the 12-volt battery be relevant? If the car was in READY, wouldn’t 12-volt power for the electronic shift lever system have been coming from the DC-DC converter?

The NTSB wouldn’t be involved; I’ve previously explained how its functions differ from those of NHTSA, which would receive the complaint, add it to their database, and probably do nothing further. Invoking either agency’s name is an empty threat.

 

Perhaps a defective 12v is affecting the charging system, as they sometimes do when trying to jump start unsuccessfully.
Or perhaps the inverter is wonky