Hi all, just got my hands on a RossTech unit so coding everything I possibly can. Recently upgraded my factory 16" steels to Springfield OEM 18's (obviously these have a larger wheel circumference). The IDE numbers verify the 16" coding but is there any mechanical reason why you'd code the circumference change into VCDS? At the moment my Speedo over reads e.g 70mph Speedo when GPS states 67 which I quite like (should never get caught speeding) and wouldn't necessarily change. I've seen references to MPG reporting and the odometer being out but again I can live with this. I'm thinking more along the lines of weather this affects indirect TPMS or AbS?
[Guide] [T6_modified] T6 Speedo Adjustment with VCDS
- Thread starter mmi
- Start date
This is an excellent write-up. I'm hoping that every T6.1 has the same variant circumferences, as all I can do is follow the same process.Despite lots of searching, I never did find anyone who'd documented this on a T6.1 (or at least posted about it). So I got brave (or foolish) one evening and decided to try it regardless and finally... success! So thought I'd come back here and post my results in the hope it helps somebody else out.
So as a reminder, my conversion was based on a 22-plate T6.1 Startline (T30 150 DSG) with optional business pack. So the OEM wheels were 16 inch steels with 205/65 R16 tyres. As posted previously, the K-number (IDE00842) doesn't seem to exist on the T6.1 and instead there's just two different IDE00845 values, one for trip distance (2066mm) and one for speed (2149mm).
View attachment 159451
When I looked at the long coding helper I could see my wheel circumference was set to variant 1 - makes sense given the 16" steels are probably the smallest wheels fitted to the T6.1 out of the factory.
So with my 275/40/20's fitted, the speedo is reading ~4mph low at 70mph (speedo = 66mph, measured GPS speed = 70mph) which is pretty much in line with what willtheyfit.com tells me.
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Now the scary part. There's plenty of evidence on various forums and in this thread that changing the wheel variant on the new T6.1 platform is a one-way street. i.e. you can increase the variant but not go backwards. So my approach was to increment the variant one step at a time, hoping they scaled in a relatively linear fashion.
Step 1 - set to variant 2. Coding was rejected (Request out of range).
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Step 2 - set to variant 3. This time coding was accepted, and my IDE00845 values were increased to 2111mm / 2195mm respectively.
View attachment 159455
A quick test drive confirmed my speedo error was reduced to about 2-3 mph.
Step 4 - set to variant 4. Coding was rejected (Request out of range).
Step 5 - set to variant 5. Coding was rejected (Request out of range).
Step 6 - set to variant 6. Coding was accepted, and my IDE00845 values were increased to 2195mm / 2294 mm.
View attachment 159456
Another test drive and now my speedo is pretty much bang on. At this stage I was very happy to call it quits. Whilst I could have tweaked it higher so that the speedo reads a little higher than actual (as is common practise), I wasn't willing to risk a large leap in circumference knowing that I couldn't revert back. Incidentally I did try going backwards just to verify, and can confirm you get 'Coding Rejected Error 22' which prevents you from doing so.
Thanks to everyone who chipped in with advice, particularly 'AudiGit' on the Ross-Tech forums (where there's a similar thread to this) who gave me sufficient confidence to go for it!
I hope this helps out anyone looking to do a similar tweak.
This is the Tyre change I need to do:
Though I think I read somewhere that some people have changed to a similar wheel and tyre size without needing to change the speedo, I wonder what wheel size they started on?
I finally was able to find some time to start this Speedo Calibration.
I've set it to Variant 3. Variant 2 didn't work just as stated before in this thread.
I took it for a test drive. But the traffic was pretty bad around here and I couldn't get a steady run anywhere at a decent speed. I'll be taking a long trip up the coast tomorrow so I'll be able to do a proper test then, to see how far out the Speedo is now. Though with the small test I did, it does seem to be still over by around 1-3km/h.
I did also find that when I stopped at the Servo for a few minutes, I did get an error light showing up on the dash that seemed to be related to the Adaptive Cruise Control. I'm assuming it's just getting used to the new wheel circumference settings. I did another Auto Scan when I got home and saved it. Then I just cleared all the errors. Hopefully, it won't have any issues tomorrow when I start my long drive.
I'm not 100% sure but I have a feeling the other error messages may be also related to the battery level at the time. I hadn't driven the van in about a week and I think the Dashcam had almost drained the battery. In Hindsight, I probably should have taken it for a drive and charged the battery up a bit before I made the Variant change but I didn't realise at the time it was so low.
I've set it to Variant 3. Variant 2 didn't work just as stated before in this thread.
I took it for a test drive. But the traffic was pretty bad around here and I couldn't get a steady run anywhere at a decent speed. I'll be taking a long trip up the coast tomorrow so I'll be able to do a proper test then, to see how far out the Speedo is now. Though with the small test I did, it does seem to be still over by around 1-3km/h.
I did also find that when I stopped at the Servo for a few minutes, I did get an error light showing up on the dash that seemed to be related to the Adaptive Cruise Control. I'm assuming it's just getting used to the new wheel circumference settings. I did another Auto Scan when I got home and saved it. Then I just cleared all the errors. Hopefully, it won't have any issues tomorrow when I start my long drive.
I'm not 100% sure but I have a feeling the other error messages may be also related to the battery level at the time. I hadn't driven the van in about a week and I think the Dashcam had almost drained the battery. In Hindsight, I probably should have taken it for a drive and charged the battery up a bit before I made the Variant change but I didn't realise at the time it was so low.
Update:
After driving on Variant 3 for a while I found that my speedo was out by 2km/h. Speedo = 100km/h, GPS=102km/h.
So I decided to continue to the next variants. Just like @JimmyAK Variant 4 and 5 didn't work. Variant 6 worked.
Now the Speedo is reading 2km/h the other way. ie. Speedo = 100km/h, GPS = 98km/h.
This is now legal so I'm happy.
After driving on Variant 3 for a while I found that my speedo was out by 2km/h. Speedo = 100km/h, GPS=102km/h.
So I decided to continue to the next variants. Just like @JimmyAK Variant 4 and 5 didn't work. Variant 6 worked.
Now the Speedo is reading 2km/h the other way. ie. Speedo = 100km/h, GPS = 98km/h.
This is now legal so I'm happy.
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Hi All,
Anybody noticed after changing the wheel circumference option via VCDS on a T6 (to suit 17's with 235/65/17 tyres) that the MFD display, gear indicator, now shows that the van is in 6th gear when actually in 5th and also shows 6 when in 6th. 1 through 4 gears, are showing as normal values.
Haven't had a chance to test cruise control in 5/6th yet.
I made this change a while ago but it is possible I never noticed this till now so I'm wondering is it a symptom of the above or something different.
UPDATE: cruise control works fine but… the +/- buttons seem to be increasing/ decreasing by 10kmh. Reading elsewhere it seems short press changes the speed by 5mph so maybe it’s just that, a bit strange though, all other vehicles cruise controls increase / decrease by 2kmh usually.
UPDATE : --------------------------------------------------------------------
Original Factory K-Number = 5 | Byte0 = 15 - Factory wheel/tyre = 205/65/16
Wheels changed to 235/65/17
First Change - K-Number = 2 | IDE00842 = 21100 | IDE80045 = wheel circ 2275mm | Byte0 = 12
With the above the Speedo was overreading by 3Kmh(100kmh GPS = 103kmh Speedo), I was fine with this as a buffer but the above problem of the current gear indicator on MFD display was showing as 6 when running in gear 5 or 6
First Change - K-Number = 3 | IDE00842 = 21868 | IDE80045 = wheel circ 2195mm | Byte0 = ? 13(from memory)
With the above the Speedo and GPS are in parity, < than 1kmh apart and now MFD current gear indicator is showing as expected, displaying 5 when in fifth gear and 6 in sixth with the proper prompt to change from 5 to 6 so all working as it should.
Hope this helps somebody out in the future.
Anybody noticed after changing the wheel circumference option via VCDS on a T6 (to suit 17's with 235/65/17 tyres) that the MFD display, gear indicator, now shows that the van is in 6th gear when actually in 5th and also shows 6 when in 6th. 1 through 4 gears, are showing as normal values.
Haven't had a chance to test cruise control in 5/6th yet.
I made this change a while ago but it is possible I never noticed this till now so I'm wondering is it a symptom of the above or something different.
UPDATE: cruise control works fine but… the +/- buttons seem to be increasing/ decreasing by 10kmh. Reading elsewhere it seems short press changes the speed by 5mph so maybe it’s just that, a bit strange though, all other vehicles cruise controls increase / decrease by 2kmh usually.
UPDATE : --------------------------------------------------------------------
Original Factory K-Number = 5 | Byte0 = 15 - Factory wheel/tyre = 205/65/16
Wheels changed to 235/65/17
First Change - K-Number = 2 | IDE00842 = 21100 | IDE80045 = wheel circ 2275mm | Byte0 = 12
With the above the Speedo was overreading by 3Kmh(100kmh GPS = 103kmh Speedo), I was fine with this as a buffer but the above problem of the current gear indicator on MFD display was showing as 6 when running in gear 5 or 6
First Change - K-Number = 3 | IDE00842 = 21868 | IDE80045 = wheel circ 2195mm | Byte0 = ? 13(from memory)
With the above the Speedo and GPS are in parity, < than 1kmh apart and now MFD current gear indicator is showing as expected, displaying 5 when in fifth gear and 6 in sixth with the proper prompt to change from 5 to 6 so all working as it should.
Hope this helps somebody out in the future.
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Had the chance to do a long solo drive at the weekend and pay attention to the gear indication. All seems normal in my van, albeit it's a T6.1 and not a T6.
Yes, this will happen with certain K number settings. Ultimately it depends on the cluster and software version but it’s known to happen as the cluster is looking for gear info for a different vehicle type. You’ll need to select a different K number to resolve it.
As long as it’s not a T6.1, you can change the settings without issue.
@JimmyAK - Thanks for the feedback..
@Lightrofit - thanks for the input, figured it was something like that but great to get some confirmation, I’ll try some different K-Number settings and report back to the thread when I get a chance. Cheers…
I know this thread is T6 specific (certainly not for T6.1), but will this work for a T5.1?
I've struggled to find a better guide. I will be using VCDS.
What I have read from other posts is that T6 and T5.1 is the PQ25 platform, and T6.1 is MQB platform.
Wondering if anyone has done this on their T5.1.
www.t6forum.com
I've struggled to find a better guide. I will be using VCDS.
What I have read from other posts is that T6 and T5.1 is the PQ25 platform, and T6.1 is MQB platform.
Wondering if anyone has done this on their T5.1.
Project 400k - T5.1 to T6.1 facelift
Hi everyone! My first post as I need some of your expertise! Technically I own a T5.1 (don’t evict me!) but I am in the process of doing a T6.1 conversion and full respray of our 2014 LWB highline. I did read about body coded parts? But I really need some help with electrical stuff. Ideally I...
Last edited:
Yes, it will work also for T5.1.I know this thread is T6 specific (certainly not for T6.1), but will this work for a T5.1?
I've struggled to find a better guide. I will be using VCDS.
What I have read from other posts is that T6 and T5.1 is the PQ25 platform, and T6.1 is MQB platform.
Wondering if anyone has done this on their T5.1.
Project 400k - T5.1 to T6.1 facelift
Hi everyone! My first post as I need some of your expertise! Technically I own a T5.1 (don’t evict me!) but I am in the process of doing a T6.1 conversion and full respray of our 2014 LWB highline. I did read about body coded parts? But I really need some help with electrical stuff. Ideally I...
Actually, the origin was a tweak for T5.1 (MY14) - as mentioned in post#1 (copied below)
Daryl_88
Member
Could anyone help recalibrate my speedo around the Essex area? Just had 245/65/17 fitted today and speedo reading 70mph but gps saying 74/75mph! Don’t mind the discrepancy being the other way around but I’ll likely end up with speeding tickets if I keep it like this .
Happy to travel and pay.
Cheers!
Happy to travel and pay.
Cheers!
ShaneMitchinson
New Member
Did you ever manage to resolve this? I unfortunately didn't read this far in the thread and changed my T6 to match the 245 65 17 tyres. It's now showing 5th and 6th both as 6th gears as you said. Changing it back to the original setting does not resolve it either. I haven't tried any other options as the one I have selected has resolved speedo.
Yes, same issue here regarding there gears.
@ShaneMitchinson - Yes, you will need to try different K-Number Settings. Have a look below. @Glenn Board
no, I still have the issue.
ShaneMitchinson
New Member
Will give setting 3 a go and see if that helps. I did change back to original setting and the gear indicator still read wrong weirdly.
ShaneMitchinson
New Member
Setting 3 has resolved gear shift indicator and speedo is bang on with GPS using 245 65 17 BF Goodrich tyres. Cheers
I have a VCDS and a 2021 T6.1 transporter. I have larger tyres on my van as I drive gravel and off road tracks wherever possible. I have had a speedo that undereads due to the larger tyres. After consulting this thread and almost no experience on the VCDS I managed to recode my wheelsize succesfully. I now have a speedo that over reads by about 2% which suits me and complies with the law. Very happy I could achieve this by using the advice given by all on this thread. Thanks to all. I think I coded variant 6, it was the first code accepted after what was originally set as variant 3.
Many thanks to this thread an the excellent guide in here, I had VCDS delivered today, I changed my wheels/tyres from std 235/55R17 to 245/65R17 which meant the speedo was over reading, odometer was under reading, and MPG figures were also incorrect due to this.
My K number settings are as below:
My 245\65 tyres have a circumference of 2357mm so I initially set the K number to setting 1. Then went for a test drive, a quick 4.7 miles each way round trip.
First thing that happened is the DSG box, when shifting down a gear when accelerating, was jerky as hell!! Then, ACC gave an error once I was above 40mph or so. And finally, I had a white spanner icon flashing where the gear indicator "D7" was. Oh and the 4.7 mile each way, so 9.4 mile round trip was showing as 10 miles on the odometer.
Got back home, read the fault codes and got a "inconceivable/incomprehensible reading from ABS sensor" as a new code, so I guessed that the setting 1 was too big of a circumference for the ABS sensor.
I then set the K number to setting 2, did the same test drive and all was good with the world! Speedometer is reading 2mph higher than GPS at 70mph (72mph for 70mph GPS), and 1-2mph over at 50mph (51mph for 50mph GPS). And the odometer is now bang on, reading exactly what the GPS distance said. And no issues with the DSG box or any errors, and ACC is working perfectly.
My K number settings are as below:
My 245\65 tyres have a circumference of 2357mm so I initially set the K number to setting 1. Then went for a test drive, a quick 4.7 miles each way round trip.
First thing that happened is the DSG box, when shifting down a gear when accelerating, was jerky as hell!! Then, ACC gave an error once I was above 40mph or so. And finally, I had a white spanner icon flashing where the gear indicator "D7" was. Oh and the 4.7 mile each way, so 9.4 mile round trip was showing as 10 miles on the odometer.
Got back home, read the fault codes and got a "inconceivable/incomprehensible reading from ABS sensor" as a new code, so I guessed that the setting 1 was too big of a circumference for the ABS sensor.
I then set the K number to setting 2, did the same test drive and all was good with the world! Speedometer is reading 2mph higher than GPS at 70mph (72mph for 70mph GPS), and 1-2mph over at 50mph (51mph for 50mph GPS). And the odometer is now bang on, reading exactly what the GPS distance said. And no issues with the DSG box or any errors, and ACC is working perfectly.
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