Distance Impluse Adjustment?

The OBD FAQ has the following entry:

Volkswagen MkIV (Golf/Jetta/New Beetle) VAG-COM Info
Updated 28 Mar. 2005
17-Instruments: K1 -- KWP-1281
[Select]
[17 - Instruments]
[Recode - 07]
Write down the existing coding for future reference.
Enter 5-digit code from below

Look at the fifth digit in the coding (Distance impulse multiplier):
2 - 3538
4 - 3648 (some 2002+ models)

Does this mean that my speedometer can be adjusted for tire or wheel size changes?

No -- unless the different wheel / tire combo happens to match up with one of the available distance impulse multipliers.

-Uwe-

Speedo inaccuracy due to different tire size/gearing can be accomodated with a Dakata Digital adjustable VSS pulse frequency adaptor.

Chris,

What would be the best way to adjust that adapter to get back to original speedometer readings? A bunch of trial and error, comparing the tach to the odo, or maybe counting the number of pulses per x number of revolutions while the car is jacked up, or what?

If you mean getting back to original speedo readings before installtion of larger tires or gearing, just readjust the adaptor to zero multiplicative correction or take it out of series with the VSS signal.

If you mean getting back to ACCURATE speedo readings, regardless of tire size/gearing (which it would never have been even from the factory), its just a matter of getting accurate speed or time/distance readings from GPS, speedo dyno, radar or known accurate mileage markers, calculating the % error, then adjusting % correction on the pulse adaptor.

Of course, beware that typical VW speedos will display pretty accurate distance values in the odometer, while displaying optimistic speedo values, so correcting optimistic speedo readings by adapting VSS pulse frequency will generate pessimistic odometer readings. This situation can be finessed by actually not using a pulse adaptor at all to correct a "normal" VW speedo (i.e., accurate odo, optimistic speedo). Correction in this case involves reindexing the speedo needle to read below "0" when at rest and verifying that resulting reading corrections are linear thoughout the full speed range.

Bump for an old topic

So, last weekend I went to a larger tire size (205/70/15) and I would like to be able to adjust my odometer so that it records the miles on the car correctly.

I searched quite a bit and found a few other threads like this one and I was able to find this location in VagCom on my car.

I seem to have 4 options in my coding and the OEM setting was 2

1 = 4345 impulses/km
2 = 3528 impulses/km
3 = 4134 impulses/km
4 = 3648 impulses/km

Since I went with a ~5.5% larger tire, I need to go with a lower number of pulses/km - ideally ~3334 - to get my odometer back to ~accurate.

All of the available coding options are the wrong direction.

If you go into the adaptation area of the instruments, in Group 16, it appears that you can change this variable to whatever you want, however I can't seem to get logged in properly with the code that VagCom suggests (don't remember it off hand). I get a "Fail" in my trip meter on the dash whenever I try it.

This thread is going on 5 years old - any new breakthroughs? Am I stuck with one of the 4 available options as Uwe mentioned or can I get logged in somehow and adjust it as I want to?

Any help would be appreciated

Thanks in advance

Try log in 13861

That sounds familiar like what VagCom suggested, but I'll try it out tonight when I get home.

Thanks!

Did it work?

I just increased my tire size on the wagon to 205/70R15s, so I also need to modify my speedo reading. Did the adaptation work?

Interested in this too...I'm tired of having to calculate out my service intervals and keep track of actual miles driven.

I'm sorry, I've been slacking and too many other things going on. I'll see if I can try the above log in this week.

Has anyone confirmed that this actually worked. Was that the correct code to use? I am going with a slightly smaller tire by about 1/2" in order to get sport style. 20 more revolutions per km.

No luck with adjusting group 16 through adaptation.

No luck with adjusting group 30 under instruments either.

I tried this tonight, after the roads cleared out a little bit.

2001 golf TDI immo 2 manual 5 speed.

My original tire was a 195 / 65 / 15 on avus wheels, I am now running a 225 / 50 / 17 on santa monica wheels.

These are the calculations for the differences:

Factory tire diameter should be 24.98031, new tires should be 25.85826 inches. Causing a difference of 3.51% less miles on the odometer.
I should be traveling 1.75728 MPH faster than the speedometer shows, since volkswagen sets it to show about 2 mph faster than actual that would explain why it is more accurate now.

I tried recoding the instruments with vag-com and the 5th digit is the one that changes speedometer readings.

there are 4 options for the 5th digit, 1, 2, 3, and 4.these were my results:

using 1 in 5th digit reads 40 actual speed 50
using 2 in 5th digit reads 50 actual speed 50
using 3 in 5th digit reads 43 actual speed 50
using 4 in 5th digit reads 49 actual speed 50

Someone in this post asked about smaller diameter tire and that is possible with vag-com. Larger tires are another story.

I tried adjusting the values for group 16 in adaptation and it would not accept any value other than the original saved value of 4345. I tried every number, going 10 numbers higher and 10 numbers lower, and it always read "error" and would not accept it.

I also tried group 30 in adaptation. Original value 128, tired every number from 120 to 136 (lowest to highest values accepted by vag-com), and while it did accept the values, it had no effect on the speedometer reading.

I would rather my speedo show 2 to 3 mph faster than actual, and have an accurate odometer like it was stock, for fuel mileage and maintenance.

If anyone has any luck with an answer to this please post it.

kbrenny - thanks for testing this out and reporting back what you found

no problem, just hope someone knows about or finds a solution to fix it and post it here.

It is apparently possible to rescale both the odometer (via K-value) and the speedometer if you have a tool for editing EEPROM (VagTacho, VagDashCom, etc.). Some information on this is found in these threads:

http://forums.tdiclub.com/showthread.php?t=184867&page=2
http://www.gti-tdi.de/board2/index.php?page=Thread&threadID=2158
http://www.gti-tdi.de/board2/index.php?page=Thread&postID=12285

Be very careful if you go this route!

From my research that is possible with 2002 and newer mkiv with immo3. For 2001 and 2000 with immo2 there is no access to adaptation for the correct channel under instruments with vag-com. This may be possible with vag tacho on immo2 but I am not sure.

I have a spare 2002 immo3 TDI cluster sitting in my garage and I am going to try using that cluster in my immo2 car with some help from jetta97.

I will post when I have tried this and let everyone know.

Let us know how it goes, I think jetta97 is definitely the right guy to go to!

Problem solved.

I did not have to use the Immo3 cluster in my Immo2 car!

Jetta97 was able to adapt my existing Immo2 cluster to work.

Jetta97 used a program called "vag dash" and was able to adapt the value of 3528 to 3355.

I am not sure what address this value was located in but I know it worked.

With the original wheel / tire setup I was doing an actual 67 when the speedo was showing 70. this is roughly a 5% difference.

With the new wheel / tire setup the speedo was dead on but threw my odometer off, showing less miles than actually traveled.

Jetta97 just decreased the value by approximately 5% (roughly the difference from stock to now) and it put me right back at factory. (actual 67 showing 70).

I was more concerned about the odometer being correct than the speedo being dead accurate.

For larger wheels and tires you would have to decrease the 3528 value by the calculated percentage of difference in tires diameter.

For smaller you would just increase the 3528 value by the percentage of difference.

With smaller diameter tires you may be able to get close enough just changing the last digit in your instruments coding to either a 1, 3, or 4. you would have to use vag-com for this but the factory setting is 2 on a tdi and all other options will only be accurate with smaller tires. No option on the coding that works for larger tires.

Changing the 3528 value with vag dash will cause the last digit in instrument coding to change to a 0 from the factory 2 (tdi). 0 was not an acceptable coding input with vag-com before this mod.

Checked the odometer using mile markers but only got to go 25 miles. It was dead on for that distance. I will try doing 100 miles later this month using mile markers but i doubt there will be any significant difference.

I have a 2000 Golf.
Like you stated, VagCom won't change my settings.
What is Jetta97? Is that more downloadable software?

Jetta ,97 is a forum member: http://forums.tdiclub.com/member.php?u=87519
brnsgrbr, you'll need a more powerful software tool, but be warned that you can (and people have) mess up your cluster if you make mistakes.

The previous owner of my car installed a FIS cluster and the speedometer seems accurate according to radar guns I pass by, but I doubt he went through the involved procedure to make sure odometer and speedo are both accurate, especially since as I received it the cluster's MFA MPG reading wasn't properly calibrated . . . I'll probably borrow a GPS one of these days and track mileage to compare with the cluster.

I switched my 09 JSW (MKV) to have larger tires, and changed the value to a smaller number (was 3=21960 changed to 4=21848).

Speedo is almost perfect.

Was 75 GPS MPH with 70 Speedo MPH
Now 70 GPS MPH with 70ish Speedo MPH

Check your odometer though. It is also affected IIRC.

Interesting...

I never validated the odometer before changing the setting.

It just recorded 76 miles when I drove 72 miles according to my GPS, though.

Oddly I would have thought it would have recorded too few miles since my tires are bigger than stock and the new setting reduced the MPH... weird...