Speedometer error on Toyotas

[i6pwr]

We've owned 3 Toyotas in the last 8 years, Sienna, Corolla, Highlander, all newer than 2005.

All of them register 2-3 MPH high, with new tires.

Am I just the odd man out or have others experienced this?

Makes me wonder if true....good standings with insurance companies but that's purely speculation at this point.

 

[Tman220]

07 Camry from 0-60 mph the speed shows 3-4 mph too high.

but seems to be more accurate at 70+

since it's not a constant percentage error I would say it's intentional for whatever reason.

 

[wavinwayne]

Both of my BMWs register 3mph high, regardless of speed, compared to Waze.

 

[Graham Piccinini]

Had many Toyota/Lexus vehicles. All show 2MPH high. Same with all Hondas I've owned.

 

[IndyIan]

I can't think of a car or any vehicle that doesn't read high by that amount? I put ~3% larger circumference tires on my Focus and its pretty much right on now. Outback is off by 3% as well.

 

[i6pwr]

Outback is off by 3% as well.

Our highlander is off by eight percent.

The four GM vehicles I've owned are all dead on, perhaps vary by 1 MPH...still have 3 of them.

 

[ArrestMeRedZ]

GM, always on in my experience. Toyota and most Japanese cars I've driven read high. I speculate it's intentional to a) void the warranty before it's normal time, or b) trick the driver into thinking he or she is getting better gas mileage than they really are.

 

[IndyIan]

Our highlander is off by eight percent.

The four GM vehicles I've owned are all dead on, perhaps vary by 1 MPH...still have 3 of them.

I think in the 2000's Honda had some off by 8-10% and some owners sued for warranty loss, IIRC, and diminished resale value? 8% is a lot.

 

[Gyro Gearloose]

My 2017 Honda truck reads 1 mph high from 30 - 75 according to the speedometer app on my phone.

 

[BMWTurboDzl]

GM, always on in my experience. Toyota and most Japanese cars I've driven read high. I speculate it's intentional to a) void the warranty before it's normal time, or b) trick the driver into thinking he or she is getting better gas mileage than they really are.

LOL. No, that's not what they're doing. They've programmed a correction factor into the speedo. It can be coded out in BMW world.

 

[wavinwayne]

...I speculate it's intentional to a) void the warranty before it's normal time, or b) trick the driver into thinking he or she is getting better gas mileage than they really are.

I don't know what trickery in involved, but on my BMWs the mileage seems accurate despite what the speedometer says. I know exactly how far it is from my driveway to my parking spot at work and the odometer on both BMWs matches this distance.

 

[supton]

Right, it's the speedo that reads high, not the odo. IIRC in Germany the OEM is responsible for speeding tickets if it can be shown that the odo is in error. Ergo, "fix" that by adding a couple kph and then they are covered. Probably more important in the days of analog speedometers, not so much today with precise electronics, but still done all the same.

 

[i6pwr]

Right, it's the speedo that reads high, not the odo

Odo is a relation to speed over time, so I can't see how they would be different.

 

[b_b]

f150 is one mph high.

 

[supton]

Odo is a relation to speed over time, so I can't see how they would be different.

While distance traveled is the integration of speed relative to time, there is nothing that prevents them from calculating distance traveled and current speed, and applying a gain to speed shown while correctly logging distance traveled.

 

[i6pwr]

f150 is one mph high

I see a trend....

My speculation on insurance would be speeding tickets....or minimizing from a statistical standpoint.

 

[i6pwr]

While distance traveled is the integration of speed relative to time, there is nothing that prevents them from calculating distance traveled and current speed, and applying a gain to speed shown while correctly logging distance traveled.

If your speedo is reading high, your logging more miles...it's not GPS based iirc.

Your PCM thinks the wheels are turning faster.

 

[supton]

If your speedo is reading high, your logging more miles...it's not GPS based iirc.

Your PCM thinks the wheels are turning faster.

If you believe that, then try this: next long road trip, something 60 miles or more, get onto the highway and drive as you normally do. Make note of the mile marker and what tenth of a mile your odo is registering (or simply reset trip). 60 miles later, recheck. If your PCM is registering wrong as you indicate, your odo (or trip) will be 2-3 miles high, to match what you are saying.

I don't think it will be, but the proof is in the pudding.

[You could do a trip of 30 miles, as you would see a 1 to 1.5 mile error. You could do ten miles instead, but now it's more like 0.3-0.8 error, which may be a bit harder to see--hence the recommendation to do a longer trip.]

 

[barryh]

Odo is a relation to speed over time, so I can't see how they would be different.

They don't need to be different but they are or were very different on purpose. Odometers have always been reasonably accurate within perhaps 1 or 2 % but speedos were permitted by law to over read typically by up to 10% but not permitted to under read at all. Manufacturers simply erred on the safe side of the law. At least that was the case historically. Modern speedos are much more accurate. My 1989 Mercedes along with most cars of that era overread by up to 10%. My more modern Mercedes seems to be quite accurate over reading by only 1 mph. I guess the much more accurate modern speedo has given the manufacturers the confidence to calibrate them closer to the real speed and still be within the law.

My 1979 BMW speedo was truly dreadful reading 37 mph at a true 30 mph and that was not untypical of motorcycles. I've recalibrated it myself to read spot on at 30mph and only over read by 1 or 2 mph fast at higher speeds. It gives me much more confidence going through 30mph speed traps.

 

[Quattro Pete]

If your speedo is reading high, your logging more miles...it's not GPS based iirc.

Your PCM thinks the wheels are turning faster.

Not exactly.

What I think @supton is saying is that the computer is calibrated to determine both speed and distance accurately, let's call it "base value," but this data is then further manipulated, let's call it "adjusted value". The adjusted value could be something simple like adding a couple of kph or mph to the base value. The car then uses base value for tracking distance, but sends adjusted value to the speedometer to be presented to the driver, for the reasons already mentioned earlier.

On my old BMW, I could access the internal computer to see both values - base and adjusted, but only the adjusted value would be shown on the main speedo.