2008 LS460 speedometer is high by 3-4 mph verified by google maps and my Garmin anyone know if there's a fix?? And if this false reading is adding miles to odometer??

 

Try going by a cop at 80 and have him clock you to verify.
Are you running stock tire size?

 

If you need another check point, I use GPS Odometer app on my iPhone, it seems to work well.

 

i have a similar problem with my ‘11 LS . When I bought this CPO, I upgraded the wheels to Lexus’ ‘19 inch sport type. While I used to think this might be the problem, the switch to low profile tires should have
eliminated the mph difference, at least to a wheel expert on Motor Week’s Goss’ Garage. I don’t like it because it incorrectly adds miles to the OD.

 

I would talk to a tire shop. Someone different than where you usually go. Have then look at your tire size. They can confirm if a change in tires/wheel size has caused this or not. That way you've eliminated or pinpointed the possible cause. Even if you're the original owner, some tire shop could have given you the wrong size and caused this issue. I agree that this could add to your odometer over time and best to get it squared away.

 

All speedometers read high - don't worry about it. It's done on purpose. If you want to go the "real" speed you desire, just go 3 or 4 miles faster than what is shown on the speedometer. That's what I do.

Your odometer is likely accurate by design. You can verify that by carefully monitoring mile markers on Interstate highways as you drive.

 

mile marker test is a great idea

 

Or plug in an OBD2 reader and check the speed reading from ECU. On my previous car, the ECU speed was practically the same as GPS speed; the actual speed is known to the car and as such the odometer and average speed are be accurate. The speedometer error is simply intentional.

 

I'm running 235/50 R 18; same size as spare tire
Sooo you mean to tell me my other car 2004 GMC conversion van which barely measures 1 mph difference is better than my LEX

 

Tire size is right, so that's eliminated as a cause. So now, is odometer off as well as the speedometer? I like the mile marker test that was suggested. Just use the trip odometer, hit reset when you pass a green mile marker and make note of the reading as you pass the next mile marker. Assuming the mile markers are accurately placed. You can also time the mile, 60 mph should be 60 seconds. Your phone has a stop watch function. I'm just guessing that Techstream software used by dealer can adjust speedometer and odometer. Toyota would likely charge you less, but call first to see if they can actually adjust your odometer/computer and how much they charge. Let us know how it turns out so we can all learn from your experience and good luck.

 

All. due respect but I've never heard that before. My other cars are an MB and a Lincoln and they are right on the rate of speed shown on radar signs in our city while the Lexus is 3 MPH or so over at 40. I will try your mile marker test and see how that goes. Thanx...

 

Any statement containing the words all/always or none/never are reflecting a black and white attitude. About the only thing I can think of that's consistent/ black and white is math. 2+2 Always equals 4, 2+2 Never equals 5.
When you do your road test, the more mile markers you use, the more accurate the test is likely to be.10 miles is more likely to reveal an error than 1 mile. Have fun with this!!

 

If your car is equipped with a GPS Navigation System, it has two odometers. One of the odometers is the one that appears in the instrument cluster where the speedometer is and keeps track of the cars total miles. The other odometer is part of the navigation system and you call it up using the navigation computer controls. The odometer that is part of the navigation system is used in MPG computations and can be calibrated to consider tire size, even to the extent of tire wear, as it impacts MPG calculations. The calibration process is an operator procedure, no tools required. Refer to your Navigation System manual that came with the car. Comparing the two odometers should give you a good idea as to the impact of actual tire size on the car's odometer.