Is250 Speedometer Inaccuracy

[fritzman81]

Hi All,

I have had my IS250 Prestige since September 2006, and from the time I picked up the car I noticed that the speedometer over read by about 8 Km/h. I had it back to Lexus in the first week for testing, and they confirmed my figures, but stated; Acceptable Variation, on the test results sheet from RACQ.

Further testing myself, has shown that although the speedometer is out by 8 Km/h across the range, the odometer over reads by only about 1%. This means that it is not just a simple ratio mismatch, but a design or programming fault within the speedometer.

I have contacted Lexus several times; however they simply quote the ADR's:

ADR (18/03): Requires vehicle speedometers to indicate a speed equal to or higher than actual vehicle speed, and no more than 10% + 6Km/h higher than actual speed.

Example: If actual vehicle speed is 100 Km/h, the vehicle speedometer must indicate no less than 100 Km/h and no greater than 116 Km/h.

There is also a Lexus Technical Newsflash, dated 26/4/2006 Ref No. LNF11/06

This basically tells the dealers to do nothing if the speedometer is within the ADR's.

Personally, I feel the ADR limit is ridiculously high, and perhaps if I had purchased a Hyundai I would expect that. But I think it is very poor for a Lexus, and is by far the worst of any car I have ever owned.

Last week I had my IS250 in for the first service. I was given a very new IS250 Sport as a loan car for the day. The car had the 18in wheels on it, it so I took the opportunity to do some more testing. I found that having the bigger wheels (plus greater rolling diameter) had slightly improved the speedometer; it was only 6 Km/h over across the range. However it had now pushed the odometer down to under read by about 1%. So it seems the same fault still exists, it has just shifted slightly.

Does anyone else have similar issues?

I also have copies of the Lexus Newsflash, ADR statement, and RACQ Speedometer test results if anyone wants a copy.

[dafidav]

how did you test if the speed reading was wrong or not?

i've never noticed this myself, but am intrigued to know

[fritzman81]

how did you test if the speed reading was wrong or not?

i've never noticed this myself, but am intrigued to know

I use a program called GPS dash, that is loaded on my PDA, and I link it to a SIRF3 Bluetooth GPS. However, you can just time the vehicle over a know distance, sometimes they have distance markers set out on major roads, if you can find some in your area.

[ldc]

It's better to be over than under cos for speed camera sakes.

[fritzman81]

It's better to be over than under cos for speed camera sakes.

Yes! But it's even better for the Speedometer to be correct.

[dafidav]

doesnt bother me that much the speedo is incorrect

as long as i dont get booked for speeding im happy :P

[sulexstu]

Hi there,

Yes i recently checked my speedo as wondered why everyone was passing me on the freeway.Sure enough my gps showed me to be about 8 kms out at 100 kph.ie need to be showing 108 kph when actually doing 100k`s & 66k`s when doing 60.Sure enough no big deal once you know except for one minor? consequence of this----you will be clocking up more k`s (albeit only 6-8%)than you actually travel.Have not as yet queried my dealer on it.H

Hi All,

I have had my IS250 Prestige since September 2006, and from the time I picked up the car I noticed that the speedometer over read by about 8 Km/h. I had it back to Lexus in the first week for testing, and they confirmed my figures, but stated; Acceptable Variation, on the test results sheet from RACQ.

Further testing myself, has shown that although the speedometer is out by 8 Km/h across the range, the odometer over reads by only about 1%. This means that it is not just a simple ratio mismatch, but a design or programming fault within the speedometer.

I have contacted Lexus several times; however they simply quote the ADR's:

ADR (18/03): Requires vehicle speedometers to indicate a speed equal to or higher than actual vehicle speed, and no more than 10% + 6Km/h higher than actual speed.

Example: If actual vehicle speed is 100 Km/h, the vehicle speedometer must indicate no less than 100 Km/h and no greater than 116 Km/h.

There is also a Lexus Technical Newsflash, dated 26/4/2006 Ref No. LNF11/06

This basically tells the dealers to do nothing if the speedometer is within the ADR's.

Personally, I feel the ADR limit is ridiculously high, and perhaps if I had purchased a Hyundai I would expect that. But I think it is very poor for a Lexus, and is by far the worst of any car I have ever owned.

Last week I had my IS250 in for the first service. I was given a very new IS250 Sport as a loan car for the day. The car had the 18in wheels on it, it so I took the opportunity to do some more testing. I found that having the bigger wheels (plus greater rolling diameter) had slightly improved the speedometer; it was only 6 Km/h over across the range. However it had now pushed the odometer down to under read by about 1%. So it seems the same fault still exists, it has just shifted slightly.

Does anyone else have similar issues?

I also have copies of the Lexus Newsflash, ADR statement, and RACQ Speedometer test results if anyone wants a copy.

[dafidav]

yep i just got my GPS unit and while driving last nite on the freeway, i set cruise control to 70km/hr and the GPS unit showed i was doing 66km

im going on a road trip soon with the car so i can test it out at 100km/hr and 110km/hr

[capey]

I also clocked 98km/h on the Princes Freeway between Geelong and Melbourne when the speedo was showing between 105 and 110 km/h. I spoke to the service manager at Lexus of Blackburn and he says that Lexus is working on a software patch to see if the problem can be addressed by reducing the variation down to +/- 3km/h. As someone else said, the good thing is that we don't have to worry too much about speeding tickets.

[fritzman81]

Hi All,

I have had my IS250 Prestige since September 2006, and from the time I picked up the car I noticed that the speedometer over read by about 8 Km/h. I had it back to Lexus in the first week for testing, and they confirmed my figures, but stated; Acceptable Variation, on the test results sheet from RACQ.

Further testing myself, has shown that although the speedometer is out by 8 Km/h across the range, the odometer over reads by only about 1%. This means that it is not just a simple ratio mismatch, but a design or programming fault within the speedometer.

I have contacted Lexus several times; however they simply quote the ADR's:

ADR (18/03): Requires vehicle speedometers to indicate a speed equal to or higher than actual vehicle speed, and no more than 10% + 6Km/h higher than actual speed.

Example: If actual vehicle speed is 100 Km/h, the vehicle speedometer must indicate no less than 100 Km/h and no greater than 116 Km/h.

There is also a Lexus Technical Newsflash, dated 26/4/2006 Ref No. LNF11/06

This basically tells the dealers to do nothing if the speedometer is within the ADR's.

Personally, I feel the ADR limit is ridiculously high, and perhaps if I had purchased a Hyundai I would expect that. But I think it is very poor for a Lexus, and is by far the worst of any car I have ever owned.

Last week I had my IS250 in for the first service. I was given a very new IS250 Sport as a loan car for the day. The car had the 18in wheels on it, it so I took the opportunity to do some more testing. I found that having the bigger wheels (plus greater rolling diameter) had slightly improved the speedometer; it was only 6 Km/h over across the range. However it had now pushed the odometer down to under read by about 1%. So it seems the same fault still exists, it has just shifted slightly.

Does anyone else have similar issues?

I also have copies of the Lexus Newsflash, ADR statement, and RACQ Speedometer test results if anyone wants a copy.

[fritzman81]

Hi All,

I originally posted my IS250 Speedo Issue back in April 2007, I had reported the fault to Lexus 1 week after I purchased the car in September 2006. October 2007 Lexus fitted my car with a new instrument cluster with "Updated Speedo Software", my car was by this time over 12 months old. I would like to report that the problem has been sorted, my speedo is now almost exact in every way.

Thank you Lexus, but it shouldn't have taken so long. And why did you fix a fault, that you tried to tell me wasn't a fault at all?

Happy IS250 Owner

[ldc]

Capey, 98km/hr and clock showing 110km/hr is quite a difference man.

I too like the fact that there is room so you don't cat caught speeding. The bad thing is you'll be piling up more Kms than you actually are as someone mentioned.

I'm wondering if by putting on 19s, the speedo might be a little closer to the real mark.

[ageg]

Capey, 98km/hr and clock showing 110km/hr is quite a difference man.

I too like the fact that there is room so you don't cat caught speeding. The bad thing is you'll be piling up more Kms than you actually are as someone mentioned.

I'm wondering if by putting on 19s, the speedo might be a little closer to the real mark.

changing your wheel size will alter your speedo readings.

[Sapphire Cam]

As I type, Lexus are fitting a new instrument cluster to my 2006 is250! I too noticed on the VicRoads Advisory Speedo displays on the Hume and Princes Freeways that my speedo was well over actual speed. No wonder I havent received any tickets from overzealous speed cameras (non-Victorians wouldn't understand!!). Even doing 65 in a 60 zone I didnt trouble the camera operators!

I actually didnt even mention the speed issue to the dealer, however I did mention that on start-up (during the 'lightsaber' manoevoure) the instrument 'needles' were making a very quiet (but noticeable) grinding/scraping sound - so they've just decided to put a new cluster in.

I'll have to watch my speed more carefully now. But from a negative, if my speedo has been out 10% (despite correct tyres and inflation) over 30,000kms, then Ive been robbed 3,000kms really! So my 30k car has only done 27k!!