P function?

As I understand, if you press the Power button first it will go to Park before powering down. Normally I press the Park button first.

 

I can confirm that I observed this behavior recently when I accidentally pressed the Power button first.

 

I have owned my Prius for 15 months and have used the Park button a total of 7 times. I usually just hit the power button to park and power down.

I also ALWAYS set the parking brake. "Park" mode on a transmission is just that, not a very good "car holder". A parking brake is a good car holder.

 

I never use the parking brake unless I park on a significant hill.

The parking brake advocates often state that "Park" on an automatic transmission is not intended to be used to keep the car from rolling. They say that it is the parking brake instead that is intended to provide that function.

So my question is... If that's true, then why do automatic transmissions even have a "Park" setting? It seems like they wouldn't need anything other than a neutral setting.

 

This is an interesting discussion.

I never use the parking brake unless parked in a steep slope. My s.o. always does.

I don't see the point as my understanding of the "Park" mode in an automatic is that it keeps the car "in gear" so that you would have to push hard enough for the engine to turn to be able to move it. For a V6 (like on my current Maxima) that would take a lot. My understanding is that stick shifts work the same. I'm sure I might be wrong!

That said how does the "p" button work on the Prius? The Prius has half the engine my Maxima has but a lot of extra weight from batteries. How hard would it be for the Prius to be pushed? and how does it keep the car 'in gear" when no gearbox exsist?

Curious!

 

"P" engages the "parking pawl", a mechanical stop which keeps a gear in the transmission from turning.

I always use "P" for two reasons:

1. Redundancy. It's silly to use just one safety system when two are easily available.

2. Consistency. I never have to decide whether to engage the brake, and I never have to remember whether I need to dis-engage it. I just do it.

 

No, on an automatic transmission, a car in "Park" is in neutral, but interlocks in the transmission keep the wheels from turning. That's why you can rev the engine with no ill results when it is in Park.

 

When you place a conventional automatic tranny in park it actually engages a gear that locks the car in place. It does not rely on the compression of the engine (like a manual tranny would) to keep the car stationary. However, using the parking brake (BEFORE you place the car in park) gives relief to that particular gear so that the entire weight of the car isn't sitting on that single gear.

I recall my mother struggling to get her '68 Bel Air wagon out of park when it was sitting on a hill (and she hadn't used the parking brake). My dad told her to use the parking brake so that it wouldn't happen in the future.

I'm sure everyone has noticed that when you put a car in park the car may move backward or forward depending on the grade of the pavement. At that point the car is, technically, safe to leave just like that.

The Prius has a similar "park" gear. It will remain stationary when in "park", but it's always a safe measure to use the parking break. Another reason to use the parking brake: The "P" function locks the front wheels. The Parking Brake locks the back wheels. Therefore you have double the "locking" power!

 

Actually, when my Prius is in "P", and I rev the engine, the car DOES rock a wee-little bit!

 

The owner's manual states that the car will go into 'park' mode if you simply power off the car from a state other than park.

As for me, I *always* use my parking brake... The parking in front of the places I've lived have always been on a downward slope -- there' something about braking, putting it in park, then releasing the brake and having the car kinda roll back into the transmission lock that had always caused me fear.

 

leave a stickshift car in neutral and you can get out and push it. you *always* use the parking brake on a stickshift.

 

Does anyone know what the Prius transmission actually does when in "Park"? How does the CVT work for putting a car in Park?

 

that's because a CVT isn't a conventional automatic tranny. What your experiencing is MG1 speeding up and slowing down. That inetia is enough to "rock" the car.

 

One other issue I've heard is using the parking brake in cold weather. This may not apply to the Prius because the rear brakes are drums. But when rear disc breaks cool down, any water on them might freeze to the brake pad. If you happen to live in areas with icy roads, there may not be enough traction to "break" them apart...no pun intended. Anyhow, I only use the parking brake on flat surfaces.

 

The only time I use the P button is when I pull into a parking space and for some reason don't want to turn off the car immediately. For example, if there is something interesting on the radio, I'd rather put the car into park than push the power button twice to get into ACC mode, and then twice again when I'm ready to leave the car. In addition, except during wet, freezing conditions, I always set the parking brake.

I've wondered about what happens when a Prius is put into neutral. The gears in the power split device are always engaged, as is the final drive chain. Is it just a programming condition where MG1 and MG2 are de-energized? If the car is going over 42 MPH, then the ICE will have to spin to keep MG1 from over-reving. I've never put the car into neutral while it was moving, but a lot of people do to help their mileage. I'm just curious as to exactly what happens.

 

FWIW:

I was in a brake replair class once. The instructor said to either use the parking brake all the time or never. Maybe more so because I live in Michgian because of the road salt. But he said this. If you use the parking brake all the time it will stay is good working order because it is used. If you don't use it very often it can freeze in place, sometimes in the engaged position. Rust and other crap can build up and not let the parking brake move freely.

I don't use it. I'm lazy I guess. Don't want that extra step. Even on a hill. I just don't think about it.

 

For some reason, maybe early PC, the emergency brake became known as the parking brake. Maybe manufacturers didn't want to scare folks into thinking their brakes could ever fail. Anyway, it's an emergency brake, no matter what it's called today to keep from scaring the weenies. It's primary job is to stop the car in case of brake failure and to dodge lawsuits by telling folks to use it in the owners manual.

THBS, Power down and watch the park button and the P light comes on before shutting down. If, as written, you want to park and leave the car powered up, yup then use the P button. Use the emergency brake for parking in Maine in the winter and eventually, whether one uses it all the time or just a few times, it will freeze and you'll be unable to move the car until you get towed or spring arrives.

I can see using it to take the stress off of the parking pawl on a steep incline, but I'll pass on those parking spots that need it in the winter. It just isn't worth frozen brakes. It's OK to cut the wheel to use the front wheels on the curb, snowbank, whatever, as a wheel chock.

Push a manual shift car that's parked in gear? Sure, if you can overcome engine compression, or if you have bad compression, or make the wheels smoke as they rub on the ground. If not, sorry charley, it isn't moving unless you pop it out of gear. That's the BEST way to park in Maine in the winter- never any frozen brakes that way.

Warm weather driving? Who cares? The brakes surely won't freeze. It's your vehicle, do as you wish. Heck, do as you wish in the winter too, they're still your brakes.

It might be worth taking a poll of northern tier state (severe winter weather states) drivers to see how many use the emergency brake as a parking brake in the winter months.

 

Thanks, Frank. I like hearing the mechanical aspects of the Prius better than anything else.

 

Word of Caution!!!

If you get tapped from behind or from the front while parked, and the Emergency Brake is not set, the Parking Pawl can be bent or broken.