What happens if you push the "park" button while the prius is in drive and in motion?

I did my driving test in the UK nearly 40 years ago and parking on a hill, starting on a hill and the three point turn plus parallel parking were all required then.

 

I had to do a hill start, parallel park, reverse into an opening on the left, 3 point turn, U turn, drive in traffic, drive in back streets, negotiate traffic lights, give way, and stop signs, change gears, check mirrors and park in a space at a shopping centre to pass my test. In the current test they can take off points for leaving a manual car in gear when parked or downshifting approaching a corner, that is stupid.

 

Where in the UK did you take the test?

 

I took mine in 1996 in Reading. The test centre is off the Basingstoke Road (I took the test before the A33 Reading Relief Road was built, so it was busier back then), then a trip through the Whitley area if I recall correctly, then north down Southampton Street, past where the Oracle now is on the IDR, up London Road (had a bit of trouble with a parked lorry that was unloading - had to get into the next lane and didn't see a driver slowing to let me out, so he was held up which the examiner marked me down for) and back round to the test centre.

At the time, you had to perform two of three prescribed reversing manoeuvres - reverse round a corner, parallel park, or three-point turn in the road. I'm not sure if I was tested on a hill start in Whitley but probably was somewhere along the line.

From here it looks like they don't use that route any more - the A33 is more convenient. (Scroll to bottom for descriptions of routes.) Here's a map of Route 1.

The current instructions to examiners say, under Control (Item 12, page 20 of the PDF), "Full use of the parking brake should be used, to prevent the vehicle rolling backwards or forwards". Under the guide to locating faults, it says:

"Handbrake.
Applying whilst in motion
Not applying where necessary resulting in rolling forwards or backwards
Allowing the vehicle to ‘creep’ with an automatic
Unable to release fully"

Under Move Off:

"Rolling backwards when attempting to move off
Not engaging a gear and attempting to move off"

(This is a general purpose driving test form and guidance, so some parts - Taxis, towing - don't apply to general car driving.)

 

Automatic transmmission have relief blow-out valves that prevent the transmission from shifting into reverse or park while moving in a forward gear faster than 5 mph. I don't know why the Prius would be any different, but I'm not willing to try. I'm curious enough to ask my dealer, however.

tom

 

The Prius is different because it lacks an automatic transmission. All it has is one fixed set of planetary gears, much like what you find in a differential. The gears are always engaged, never shift, and never clutch out. The variable gear ratios are really just changes to the fields in two electric motor-generators.

Tom

 

Pssst, this is a little dirty secret. This sets the car into "unintended acceleration" mode :madgrin:

 

just a message in this old thread I've just read: you guys are crazy... BUT answer the exact questions that I also have! I like it.

 

[Tom,

If no blow out valve, then surely there must be an electronic blockout from preventing the gears from slipping into R or P if moving faster than "X" amount of speed.


Happy Motoring!

 

Sigh. Here we go again. The Prius has no movable gears to slip into R, P, Warp, or Time Travel mode. The Prius doesn't shift gears. It can't shift gears. Those little suckers are tightly locked together all of the time.

The Prius does have a parking pawl. A software lockout keeps the pawl from attempting to engage at any but the slowest speed. Likewise the control software will not attempt to power MG2 backward when moving above a crawl.

The control software refuses to do anything potentially harmful to the HSD: Command R while moving, the car switches to N; command P while moving, the car switches to N. These, by the way, are important safety tricks. The quickest way to remove power from a Prius is to press Park or shift to R.

Tom

 

Thanks, now I can get to sleep tonight knowing what happens if Iwould accidently press the power button or the park button. I haven't slept a wink since getting my Prius worry about this big problem!

 

You know it is all outlined in the manual right? Could have save countless hours of insomnia.

 

Force is 100% correct as I can verify. Once when I had a car accident I then pulled the car off the road and was so flustered I hit the park button when it was still rolling maybe 2-3 miles an hour and it engaged and wasn't good. Didn't do any damage apparently though.

 

My vss is out and my speedometer is showing 0 all the time. If the park button gets pressed for any reason how would the car react? I don't want to find out but I'd like to know...

 

what is vss?

 

Vehicle Speed Sensor.

Posted via the PriusChat mobile app.

 

won't be a problem

 

How would you know that? If the car thinks it is going 0 mph, it probably thinks it's okay to activate the parking pawl. At least that is the side of caution I'd err on.

I also probably find out why the VSS was broken and fix it ASAP. But that's just me.

 

The vehicle speed signal is generated by the brake ECU based on the four wheel speed sensor inputs, and is repeated by the combination meter. Other gadgets in the car that rely on the VSS are getting the repeated version from the combination meter. Some other ECUs in the car also just get the speed by asking the brake ECU over CAN.

If I remember right, the speed displayed on the combination meter, it gets by asking the brake ECU over CAN (even though the combination meter also receives and repeats the VSS).

So if the meter is displaying 0, it seems like there's a network communication issue, or an issue quite early in the brake ECU's use of the wheel speed sensors.

When you can or can't shift will depend on what the HV control ECU thinks the speed is, which I think it also gets by asking the brake ECU over CAN.

I would try a little experiment that's easier on the car than trying P. Just get the car going forward and try shifting to R. Normally, that will be allowed from around 6 MPH on down, but at higher speeds, it will beep and shift to N instead. (Do you have some way, besides the combination meter, to know how fast you're going forward?)

If you are able to shift into R from a higher speed, say 9 or 10 MPH, then I'd conclude the HV control ECU really isn't getting speed information.

Unlike experimenting with P (which mechanically shifts a pawl and will make a hard bonk if shifted at speed), shifting to R only reverses electrical power to the motor, and happens very smoothly. The car, of course, is programmed not to let you do it above 7 MPH or so, but I don't think giving it a try at 9 or 10 will hurt anything, and you will find out whether the HV ECU knows the speed or not.

Then you can infer that the same answer would apply to P.

 

Few brave souls, or rich ones.