[ArgonautVans]

Ha, maybe you shouldn’t get your speedo changed then. I’d rather have a speed that’s off, and be able to go 87 mph, than a speedo that’s accurate, and only go 81 mph.

plus, you get 7% longer warranty!

 

[Chillis]

I'm going to get cracking on this again with HP Tuners. They gave me instructions but I've been busy and then the van went to the body shop.

Now that I'm back to tuning and using the software I'll gather the data for HP Tuners to go over so they can see where the data disconnect is where the information is not changing after adjustments are made to the speedometer table.

It ain't over yet!

 

[ArgonautVans]

Speedometer recalibration - it helped more than I expected!

So I took my van for an alignment check at the same shop who installed my lift kit and larger tires last year. The guy offered to adjust my speedometer with Ford Scan at the same time. I am really glad he did it! In addition to having a more proper readout, it seems like it helped with the...

www.fordtransitusaforum.com

FYI for people reading this thread - I talked with Syncocrock. Turns out his speedometer is 3 mph slow at 65 MPH… exact same as my van was before and after trying to reprogram ~6% slow with 245/75r16 tires).

So Sierra adventure vehicles did not successfully reprogram his van either. Other than possibly the TCM which helps transmission shifting - but not speedometer or odometer.

 

[Tuckie]

 

[Whoknows]

FWIW its worth - This guy claims success on another forum on his 2017.

Ford Transit Speedometer Calibration

This may be interesting for Ford Transit owners who have upgraded to larger tires... the newest version of FORScan (2.3.29 beta) has added the ability to access a bunch of parameters in the BdyCm Central Configuration (Main) module of the Ford Transit, in particular Tire Circumference. We...

www.classbforum.com

 

[BillsPaseo]

FWIW its worth - This guy claims success on another forum on his 2017.

Ford Transit Speedometer Calibration

This may be interesting for Ford Transit owners who have upgraded to larger tires... the newest version of FORScan (2.3.29 beta) has added the ability to access a bunch of parameters in the BdyCm Central Configuration (Main) module of the Ford Transit, in particular Tire Circumference. We...

www.classbforum.com

Yeah, that was me, and several years ago. I would qualify it as a partial success. My speedo is still off by about 2 MPH at 65 according to my GPS. Before making the change in FORScan, it was off 5 MPH.

 

[klp]

Well this is something I had not considered. I can deal with speedo/odo being off but any lights on the dash means I cannot pass annual inspection in Ma. I still have stock tires on my '15 van but had hoped to get something bigger when they wear out. Is everyone on bigger tires running around with an ABS light on?

 

[asdrew]

I still haven't spent enough effort to really pursue getting rid of the lights, it probably is just one elusive parameter that need to be changed in addition to tire circumference.
If you want to get the speedometer right and live with the lights, do so. Before you take it in for inspection, just change the parameters back and clear the codes.

Also, Forscan added yet another tire circumference and after setting my van to that the speedo is spot on.

 

[klp]

Got it, thanks. I thought the light came on right away - it is only on if you reconfigure the speedo.

 

[Whoknows]

Well this is something I had not considered. I can deal with speedo/odo being off but any lights on the dash means I cannot pass annual inspection in Ma. I still have stock tires on my '15 van but had hoped to get something bigger when they wear out. Is everyone on bigger tires running around with an ABS light on?

No abs light here. 270s

 

[johnny_honda_]

Wanted to add my input to this thread in case anyone out there is searching. 2021 AWD Transit 150, finally ran the factory tires down and just upgraded the tires to 255/70R16 BFG KO2s. I attempted follow some youtube videos showing how to reprogram the tire circumference, who's default value for my van was 2164 mm. Which is about 3% less than the spec for 28 inch tires (2234mm). The 255/70R16 BFG KO2s are 30.1 inch diameter (2402mm circumference) so I programmed the tire circumference to be 3% less which 2330 mm.

I was immediately met with AWD fault Service Required. Using the latest version of Forscan (at time of writing is v2.3.62) I was able to do the AWD relearn, and that did make the AWD P160A code go away so no dash lights anymore. However, I do still have code U0422 from the PCM, but no CEL lights. I can't seem to get that one to go away.

The van drives fine as far as I can tell, but the speedometer is still a bit off. I tried to program the tire circumference to the actual value to see if that would help, Im not sure it made a difference, now at 60, I see 62 from my GPS, so maybe it closed the gap a bit? It's hard to tell. If anyone knows how to get rid of U0422 that'd be awesome I'll continue to research.

 

[johnny_honda_]

Just let me know what I need to grab from it.

It would be interesting to know what is the factory tire circumference programmed for the BCM on Transit Trail, and what are the stock tire that come on it?

 

[johnny_honda_]

After some debugging and doing some more research on the topic I wanted to add a couple more datapoints from testing and reading.

1. As of December last year, it looks like the programming for different tires sizes hasn't even been done (by the factory/engineering) on the Transit Trail: https://www.fordtransitusaforum.com/posts/1277254/
2. It appears that the Ford software has some predetermined "valid" configurations for tire circumference, otherwise you get U0422: How to use FORScan to adjust tire size - Page 3 - FORScan forum

The question remains for me is: does the tire circumference parameter actually affect the speedometer. I just set mine back to the factory number 2164 mm, and I'm about to go road test it and see if it's off from when I set it to the actual tire size for BFG 255/70R16. I will report back if I see a difference. For consistency I am testing cruise control at 60mph, for several miles and looking at my external GPS.

 

[ArgonautVans]

Seems like intercepting the wheel speed sensor data and tacking on and extra % might be the only way to tackle this problem

 

[johnny_honda_]

Final update on my previous post.

I did two tests,

1. Programmed the tire circumference to factory settings 2164 mm (no codes)
2. Programmed the tire circumference to a way higher setting 2500 mm (U0422 code is thrown).

Road tested with cruise control 60mph in both scenarios above. Identical results (2-4 mph over @ 60 mph for several miles) so changing the tire circumference on the 2021 Transit AWD does nothing. In both cases I did the AWD module relearn to get rid of the P160A code.

One interesting side note that when driving the van with U0422 active the little screen in the cluster shows which gear the van is in X/10 while driving. When the code is not on, in the case with factory settings for tire circumference the current gear is not shown in the cluster screen. Not sure why this is the case.

So it seems to me, the engine computer just doesn't recognize the change. Another thread I read user @kevvyd (https://www.fordtransitusaforum.com/posts/1295127/) mentions that you need may need to do a relearn on the TCM immediately after changing the BCM tire circumference parameter, however when loading up Forscan for my van I don't even have the TCM module showing (using wired ODBlink EX), so I'm not sure how to even try this.

It's funny to me that even transit trails from the factory have a mis-calibrated speedometer, which makes me think even Ford themselves haven't worked out the parameters for Transits at this point.

 

[njvagabond]

It's funny to me that even transit trails from the factory have a mis-calibrated speedometer, which makes me think even Ford themselves haven't worked out the parameters for Transits at this point.

I suppose they could issue a recall to put the stock sized tires on the Trail.

 

[johnny_honda_]

I suppose they could issue a recall to put the stock sized tires on the Trail.

Not sure if you're being sarcastic but didn't this already happen? Ford's Transit Trail Recall Fix for Tire Rub Is Just Installing Smaller Ones I suppose it's for rubbing on the inside of the fender liner and not the speedometer.

 

[njvagabond]

Not sure if you're being sarcastic

Moi?

 

[NarwhalPDX]

I suppose they could issue a recall to put the stock sized tires on the Trail.

Too soon!

 

[johnny_honda_]

Just wanted to drop this here, and another point of reference: How to use FORScan to adjust tire size - FORScan forum Sorry if this has been covered already.

From the first post:

Note 1: this article is actual for new vehicles with so called Economized Central Configuration (ECC). ECC means that some memory blocks in BdyCM module of the car are reserved to store parameters that are used by several modules. Tire Size is one of such parameters. Although it has been stored in BdyCM, it is actually used by PCM, TCM, AWD, ABS etc. There is some specific in managing ECC, reviewed below.

Note: some modules have a harcoded range (min…max) for the tire size. So if new value is out of the range, module will not learn it but throw P1635, U0422 or similar DTC. Unfortunately, in such cases we have no choice other than adjust the new size to be in the range (so, find maximum circumference accepted by the module).

So basically these hardcoded mix max values would have to be changed, which would probably need to be done via the as-build, and modifying the hex values directly in the other module to accept the tire circumference (which I'm not knowledgable enough to do at this moment)

Anyone following khappen to know the max value that can be used for tire circumference on the transit with throwing codes? I didn't test, and I'm probably too lazy to try to increase it 1mm or 10mm at a time until it start throwing codes.