Summary of problems reported on Prius 2010

Thanks to Ken1784 we know why the speedometer is either right on or fast. It's due to a U.N. regulation:
http://www.unece.org/trans/main/wp29...gs/r039r1e.pdf

Check this thread posts 25, 26, and 27:
http://priuschat.com/forums/gen-iii...66149-2010-toyota-prius-fcd-inaccuracy-3.html

 

Here are two more items: Brakes: traveling at creep speed I've twice experienced touching the brake LOCKS the brake. Nothing modulated about the response of the car. It's as if you'd pushed the park button.

Also brakes associated: Red light ahead, off on the gas and very light brake, and the display properly shows energy flowing into the battery. Then after stopping, or at creep speed, energy flows battery to motor. Light brake pedal brings the car to a full stop but display shows energy continuing to flow to the motor. FIRM brake pedal turns that energy flow off--but there's nothing finessed about that firm brake. I think that setting is at way too crude a level for this sophisticated machine.

 

Could this be related to incorrect MPG readings?
If Speedo reads high, does Odometer read high, also? If Odometer reads high, would MPG read high?
Or, not?

 

Tumbleweed,
Both my 2008 Sienna and the 2010 Prius show up 2 mph slow on these radar devices. It is very consistent. I did a quick check. Look for the mile markers on the side of the highway. Set the cruise to 60 mph. Pick a mile marker and time how many seconds it takes to reach the next marker. At 60 mph it should tame 60 seconds to go 1 mile. I found both vehicles are very close to 60 seconds. I believe the radar units have some kind of offset for the display that reads 2 mph lower than the measured speed.
Bob

 

We have also experienced the problem of the brakes abruptly grabbing, which is discussed by us and others in a thread on PriusChat ("Braking in Reverse").

 

the auto-dimming mirror does NOT work as designed....

 

This is by design and is true of almost all cars... New tires have a larger circumference which will overestimate the actual speed. As the tires wear down, the smaller circumference will give a more accurate speed.

 

That is not enough to account for the speed differences that are seen.

Almost all speedometers will read fast on almost all cars. Manufacturers can legally make the numbers appear higher (IE the car is going faster then the speedo says) but if they do the opposite then they are breaking laws and even UN regulations.

Most cars are 2-5mph high depending on speed.

Also if your speedo read low you could (try to) sue your car company for getting a ticket, while the opposite is legally allowed (you cannot sue your car company for wasting your time!).

So this is not a Prius problem.

 

UN Regulations?

UN can make recommendations, but in the US, at least, nothing the UN does is legally binding.

 

The Prius tire is ~25" in diameter. Circumference=2Pi*r (r=radius which is 1/2 diameter). so 2*3.1412*12.5=78.5 inches... There are 5280 feet in a mile or 63360 inches...
63360/78.5=807 revolutions per miles on the a new tire....

if tread depth is 1/2", the radius is 12" when the tire wears out. so 2Pi*r is now 2*3.1412*12.=75.3 inches... 63360/75.3=841 revs per mile, so a new tire gets 34 revolutions more per mile. 34x78.5 or 2669 inches or 222.4 ft... 222.4/5280=0.042...

so the new tire will show a 4% difference in speed... 4% of 55 mph is 2.3 mph difference between the new and old tires...

 

Traction control warning light occasionally comes on when it should not, especially stopped on flat surfaces.

http://priuschat.com/forums/gen-iii...6952-slip-indicator-comes-when-full-stop.html
http://priuschat.com/forums/gen-iii...6320-skid-indicator-light-intermittently.html

 

Not a bug, but a feature. Hill Assist. It's in the manual.

 

This is not hill assist.

When engaging hill assist the warning light flashes and beeps to let you know you have engaged it.

This issue has no beeps and the light stays on constantly.

 

Main Fluorescent Display dims way too much when you turn on the running lights or headlights on my 2010 Prius II. It is almost un-readable in anything but total darkness. The light-level adjuster only reduces it further. I'm sure you can program the default level of the auto-dimming of the display with lights on - with the factory programming program. My dealer agreed that it is way too low, but didn't know if they could fix it. (two people corroborating!)
Anyone else find this a problem?

 

They either need to find a way to adjust it or replace the bad part for you. Not having instrumentation at night is a fairly serious safety defect and you might mention that to them.

I just went out and checked mine. When I turn the lights on I can adjust the displays from full bright which is up past the click down to nothing. Both the instrument display and the Multi Function Display dim by about the same amount just as you would expect.

 

The nav voice is difficult or impossible to hear when the stereo is on...there is no option to dynamically adjust the stereo and/or voice volume while the voice is speaking.

http://priuschat.com/forums/gen-iii...nt-hear-nav-voice-over-stereo.html#post937199

 

Deleted, I'll post it in the other thread.

 

I'd really like the NAV to be added to this. very disappointed with it , so much so if i am really need it I will just use the portable garmin.
For the money we should be getting something that works properly, or at least have a choice.