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So I have been having my suspicions that the needle on my Speedometer is not accurate. So here's what I did: I used Google Maps Navigation with the option enabled that shows your travel speed. On my Sienna, it is off by 3 MPH. So if the Needle is at 50 MPH, the GPS says I'm doing 47. I did the same test on my other car, a CR-V, and the needle and GPS are spot on exactly.

Could this offset be because I had my transmission replaced? If so, would any of you suggest going to the dealer and having them attempt to fix? I feel like I may be using alot of my time, as they may probably need to take the van for a few days.

Anybody else want to try the Google Maps GPS MPH? I have the 2017 XLE AWD model.
 

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Yes, the Speedo on the Sienna is off by 3 miles. This is the same for my 2011, 2015, and 2020 Sienna. They are all off by 3 miles.
 

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My problem is that my odometer has extra miles on it because of the inaccuracy. A 20 mph trip adds 3 miles to every hour. 1000 hours is an additional 3000 miles.
 

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Does the slow Speedo affect the Odometer? I didn't think they were linked. When I measure the distance traveled against the GPS it was correct on the Odometer. Its just the speedo is slower I thought.
 

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noticed similar in our 2017 LE, with the stock 17" tires the speedometer would read a few km/h faster than the speed shown on our Garmin GPS (i.e. van 103 km/h vs. Garmin 100 km/h)

when i use my summer wheels running 245/45/20 tires, both the van and the Garmin show the same number.
 

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Very typical across all vehicles. There is no “fix” the dealer will offer because it’s built that way on purpose.
 

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My experience with our 2nd gen Siennas is that, yes, the speedometers would display 2mph faster than the actual speed. You can hook up a scan tool and see the speed the computer really thinks the van is moving at.

I believe this is due to slight variations between models of tires and between new vs worn tires, and Toyota's working assumption that overreporting speed is safer than underreporting it. Even just for new vs worn -- there is about a 2% difference in circumference between a brand new (11/32nds tread) and a legally worn (2/32nds left) tire, which will show up as a 1.2mph difference at 60mph.

When we got our new tires for our 2008 last fall, the speedometer reading ended up being spot on (and the scan tool reading would read 2mph low). But our 2006 reads 2mph fast, even though the tires are only partly worn.

- G
 

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im planning on remedying this with new wheels and tires when the current tires are worn out, witch is pretty soon. im just gonna up size a little. my 2009 is the same, about 2 or 2.5 mph off.
 

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I went with General Altimax RT43 on our 2008. The speedometer was accurate with those tires installed. I wouldn't recommend going with a nonstandard tire size.

- G
 

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Every Toyota I've driven were 3 mph faster than the actual speed. I own a 2008 Sienna and a 2019 Prius Prime plug-in and both are off by exactly 3 mph. Their odometer readings are accurate because I've tested them using the highway mile markers. I had a 1997 Mitsubishi Spyder GST which was also off by 3 mph 🤨
 

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Used to make me crazy, my wife thought I was crazy. Proved it with the Waze app. Didn’t realize Google Maps also did this. Since they now own Waze it makes sense I guess. Thanks for that. I know it’s always going to be 3mph off, but psychologically I prefer the app to my speedometer at this point, particularly on highway trips 😄
 

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My speedometer is not off by a fixed MPH amount, it's off by a percentage of the speed I'm going. It reads about 5% high, so when it says 60, I'm actually going about 57. When it reads 40, I'm actually going 38. I've verified this with several different GPS units, a speedometer app that uses the GPS in my smartphone, the radar display screens that are sometimes set up by the side of the road, and with a police radar (asked a helpful officer to clock me as I drove by holding my speed steady).
 

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Our 2015 Sienna XLE has a brand new set of Michelin's in the recommended size and I'm getting a consistent 2MPH off at all speeds verified by GPS using the GPS Status App on my phone. Same as others when I show 70 on the Spedo GPS shows 68. We just upgraded from a 2004 and it was spot on.

From what I am reading there's nothing that can be tweeked in the software to calibrate it?
 
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