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Post by sgoring03 on Jan 17, 2023 14:40:48 GMT
Firstly, sorry I know this topic is discussed elsewhere on the forums, but I can’t get the ODBEleven to change the value.
I have an A3 Cabriolet running 225/40R18’s which if I use the “factor” of 0.985 x circ for the setting this gives me 1976mm. In the “dashboard” module for wheel Circ it is set to V2 and looking at the “Live data” this shows 2002mm for circ which is the actual (not the 0.985 value)
Hence my Speedo reads high by about 9%
I have tried to change the value in long coding - I want to try V6 based on a posting about a Mk7 golf but I keep getting - marginal value not set error. I have tried with “Hood/Bonnet” open park brake on and off. With no luck. I tried with security mode but this didn’t help either.
I’m concerned the dongle is not correct as the Long coding in Dashboard also says AWD - set to “No” when my car is a Quattro. Any clues from anyone ?? I have tried OBDeleven help and they suggested the park brake issue.
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Post by dv52 (Australia) on Jan 17, 2023 22:38:48 GMT
sgoring03 : Hi. You are most certainly NOT the first to have experienced this problem and there are many similar posts on various forum about this matter related to MQB platform cars (like your Audi A3 8V). And this issue has absolutely nothing to do with a "dongle [that] is not correct" - many have experienced the same behavior using other diagnostic devices. So-it ain't a fault with the operation of OBD11! Alas, it seems that the restriction on changing the values of Byte 3, Bit 0-3 on the hex17 module is a deliberately designed phenomenon by the good Burghers on the Audi mother-ship. There isn't anything official in the pubic domain, but my personal opinion (my wild guess, really) is that there is a link between this matter and the hex17 module's security mechanisms related to the anti-tampering protocols for the car's odometer reading (I'm more than happy to be proven wrong).
Now, I'm definitely NOT suggesting that you have nefarious motives - but truth is that speedo-calibration using this method does impact the car's odometer. The extent of impact on traveled miles/km is of course dependent on the setting chosen, but over the life of the car, it can result in a significant reading difference (I reckon).
So, my understanding is that where the hex17 module does permit variations in the "wheel circ." value via the long-code software switches, it is ONLY in ONE direction. And not surprisingly, this direction has the effect of increasing the odometer reading!! This means that if a user changes the factory value, he/she can't revert the wheel circ. back to the factory value!!
Don
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Post by sgoring03 on Jan 17, 2023 23:21:16 GMT
Hello Don,
Thanks for the detailed definition and answer, my guess is the first owner of this car changed from the stock 17” to some Audi 18”s. But forgot about the 0.985 factor.
It’s very strange as the values for wheel Circ and odometer are very different in live data for its current setting as V2.
Anyway I guess I will live driving 77 indicates in a 70 without too much trouble.
Don, do you have any idea why it would say AWD - No in the dashboard module when I have a Quattro ?
Thanks Simon
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Post by dv52 (Australia) on Jan 18, 2023 0:35:58 GMT
Simon: I'm not sure about your suspicion regarding the original factory 17" wheel setting - but the point is probably moot because changing the software switches in the long-code string so as to give a smaller wheel diameter ain't permitted by the module!! As for the AWD setting in the hex17 module (I assume Byte 4, Bit 7)- I've seen lots of examples of similar "inconsistencies" on many optional functions on MQB platform cars. As a general response where this occurs, the guiding question as to what to do is: are there any error messages reported on a SCAN report, or displayed on the car screen related to the function? If the answer is No - don't change the long-code setting!
So, again my very unofficial, wild guess, hypothesis is that occurrences of this type of inconsistency results from variations in module firmware updates (sometimes called "module dataset"). My hunch is that newer software versions of module firmware happens at different rates for different modules. This means that peripheral modules to the primary module have to accommodate more than one firmware version. For AWD, I suspect that some dataset-versions in the module that controls the Haldex pump requires the dashboard module software switch to be set and some do not require this!
But again, I stress that my hypothesis is very unofficial - it's just the machination of a meandering and a very ill-disciplined mind (i.e. it's a sheer guess)!!
In any event, the important message in my response is don't change anything if the car's self diagnostic system says "it ain't broke" !!
Don
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Post by sgoring03 on Jan 18, 2023 1:44:43 GMT
Don,
Thanks again! I will try your suggestion for the cabriolet roof, and then having already done Scandinavian DRL and cornering lights I think I’ll be done with mods.
Simon
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