2010 Toyota Prius FCD Inaccuracy

[walter592]

Can any of you guys check the accuracy of your speedometer? Mine is a full 3% off (on the fast side) which will only get worse as the tires wear. Funny thing is my scanguage is 100% accurate to my GPS... It really sounds like Toyota is trying something fishy here, this isn't rocket science. I'm sure my mileage is off by at least that amount as well.

[LRKingII]

Originally Posted by walter592

Can any of you guys check the accuracy of your speedometer? Mine is a full 3% off (on the fast side) which will only get worse as the tires wear. Funny thing is my scanguage is 100% accurate to my GPS... It really sounds like Toyota is trying something fishy here, this isn't rocket science. I'm sure my mileage is off by at least that amount as well.

Garmin shows 65mph and Prius shows 64
Local radar check shows 34 when prius shows 35.
Close enough for me

[ken1784]

Originally Posted by walter592

It really sounds like Toyota is trying something fishy here, this isn't rocket science. I'm sure my mileage is off by at least that amount as well.

The speedometer offset is intentionally produced to meet the regulations.
The odo meter reading is completely different story from the speedometer.

Ken@Japan

[walter592]

Could you explain the regulations that require a speedometer to be intentional wrong?

Originally Posted by ken1784

The speedometer offset is intentionally produced to meet the regulations.
The odo meter reading is completely different story from the speedometer.

Ken@Japan

[ken1784]

Originally Posted by walter592

Could you explain the regulations that require a speedometer to be intentional wrong?

http://www.unece.org/trans/main/wp29...gs/r039r1e.pdf

Ken@Japan

[a priori]

Originally Posted by ken1784

http://www.unece.org/trans/main/wp29...gs/r039r1e.pdf

Ken@Japan

Thanks, Ken.

I think the particular language of interest from the United Nations regulation is the following:

"5.3. The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship between the speed displayed (V1 ) and the true speed (V2).

0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h"

[tumbleweed]

Originally Posted by a priori

Thanks, Ken.

I think the particular language of interest from the United Nations regulation is the following:

"5.3. The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship between the speed displayed (V1 ) and the true speed (V2).

0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h"

Interesting, according to that formula if the actual speed is 70 MPH (for example) they think it would be OK for the speedometer to read from 70 to 79.5 MPH? do I have that right? If so it would be way to much tolerance for errors in one direction and none in the other. I don't understand the logic. Do they really think a speedometer that always reads fast is somehow magically going to keep me safe? Wouldn't it be more reasonable to simply say indicated speed should be equal to V2 + or - .05 V2. After all the chances that replacement tires are going to be larger or smaller are about equal.

[dethier]

I just did my second fill-up on my 2010 Prius II. The display said I was doing 62.5 mpg, I used exactly 5 gallons for 305.8 miles, so actual mileage was 61.2 mpg. Not much difference.

Originally Posted by msirach

I started a new thread for the updates specifically for the issue of the inaccuracy of the FCD (fuel consumption display) on the 2010 Toyota Prius.

We have about 4500 miles on ours and on every tank the hand calculated MPG is off 3 to 7 MPG from what the FCD reads. My wife gets about 54 MPG on the FCD and her tanks are usually 4 to 5 MPG less calculated. Last week I had two 500 + mile fills and The first was 5.5mpg less and the second 7.1 MPG . This was with a FCD display of 62 MPG which included a lot of around town in Madison for Hybridfest Green Drive Expo. The second tank read 64.4 MPG and it was fully highway driving. It was off by 7.1 MPG .

5 to 10% is out of the box for error. I fill up at the same station, same pump, same number of clicks, and same direction each time with the exception of the fill in Madison last week of which I estimated slope to be the same at the station I filled at.

I stopped at the dealer and had them check it out to get a paper trail started. Nothing was found so I followed up with a call to start a claim with customer care the next day. They took my information and later that day, Heather from customer care called back. She gave me a file number to record to use if I called back. She was going to investigate and call me back this week.

Heather just called back and said she had talked to field service reps and engineers and they informed her they were aware of an accuracy issue of 8% to 10%. They were looking further into the issue and expected something would come out in the form of a TSB.

Once again I am impressed by the quality of Toyota's attention to their product.

[FireEngineer]

Just filled this tank.



Car took 12.075 gallons of gas. That works out to 66.28 MPG. The discrepency is 7.52 MPG which is 10.2%. That shouldn't be. My ScanGage was a lot closer for MPG.

Attachment 17253

And it had the gallons used almost dead on.



Wayne

[DaveinOlyWA]

once again the discrepancy. but still a very nice tank Wayne!!