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Author Topic: Softcoding / Distance Impulse Number  (Read 15910 times)
canigetawitness
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« on: August 05, 2015, 07:21:14 AM »

Hi I have tried to adapt a VDO 1J5 920 926 C cluster to a Bosch 1J0 920 926 C which I was assured should be compatible.
However when I went to transfer the softcoding 01414, it refused it. I read soemwhere where sometimes it won't accept the last digit and to try a 0. So I changed it to 01410 and it worked. But I see this affects the speedometer calibration so obviously it needs to be the right number.
So I wondered if anyone might shed some light on why that last digit of the soft coding can't be set to 4 on this cluster, or if there's any way around it.
Thanks.
« Last Edit: August 05, 2015, 07:54:59 AM by canigetawitness » Logged
canigetawitness
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« Reply #1 on: August 09, 2015, 08:36:40 AM »

Update: I managed to hard code the last digit in before doing the adaptation. It seems to have taken and now the speedo is much closer to the correct speed, but is reading slightly too fast compared to my Tom Tom. e.g.It reads 30 mph for 27 mph on the Tom Tom. Seems about 10% out though I've not tested it at higher speeds.
Should that even happen if the last digit matches what it was on the old cluster?
Thanks.
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ddillenger
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« Reply #2 on: August 09, 2015, 08:40:31 AM »

You are under the assumption that the factory calibration is accurate. That is false.

Is it 10 percent? Or is it a fixed delta?
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canigetawitness
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« Reply #3 on: August 09, 2015, 09:20:28 AM »

Thanks for the response.
Well this is my first run in with speedos but I was certainly under the assumption speedos should read the correct speed.
But other threads say they can be a bit over - someone mentioned 5%. Still 27 mph fo 30 mph seems high.
I'm not sure what "a fixed delta" means. But I wonder if you're asking if it's reading high by a set amount or by or a relative amount?
If that's what you're asking then that is a good question and in all honesty it was tricky to ascertain that on the test run. I think I'd need to get it up to higher speeds to answer this. There were too many cars around last night and it made it difficult to get through a good range. May take it out later when the roads are(hopefully clearer).
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canigetawitness
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« Reply #4 on: August 09, 2015, 04:09:33 PM »

You are under the assumption that the factory calibration is accurate. That is false.

Is it 10 percent? Or is it a fixed delta?
OK it proved very difficult to do a test on the motorway - busy, people driving dangerously badly, Tom Tom just refusing to work. But I managed to work it through the lower ranges again anyway, and again afterwards. It's hard to know what to say about this. It seems to work through a range of 0 -3 mph from 0 to 60 but while it's ~1 difference at 10, maybe 2 at 20, then it seems to remain at about a 3 mph differnce from 30 to 60. Which doesn't make a fat lot of sense to me. Someone suggested an output test so will try that.
I'm also wondering from some of the other errors I've been getting if my ECU may need rebuilding. The root cause of all this was an immobiliser activated message that started right after I had a coolant leak and the mechanic fixed it. I don't know how but I think somehow, the ECU or leads going to may have got wet. I did a check of the leads going in a couple of times and looked tip top. Couldnt get the ECU out of its housing, then did and couldnt get it open without forcing it cos I didn't know if that could do damge or break an important seal or something. Guess it's time to force it though. But before I came across these error messages, elimination and googling had led me to believe it was bad soldering in the cluster, hence the replacement.
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adam-
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« Reply #5 on: August 10, 2015, 06:19:29 AM »

A 3mph discrepancy really isn't that bad tbf.  Assuming you still have stock wheels, stock tyre sizes and operating at the correct pressure, a discrepancy will always exist.

I've also heard (although probably bullshit), that the factory speedos should always read higher than actual speed - so that you think you're doing 30, when infact you're going a little slower.

You can vary the speedo calibration:
http://nefariousmotorsports.com/forum/index.php?topic=7964.15

"Very important thing if you want to have accurate speed and distance readings is to properly set K value. If your cluster is set to use gearbox sender as speed source (as there are clusters which use ABS as speed source by default and you can change most clusters to use it) you can calculate proper K value using your wheel diameter. You need to calculate how many rotations your wheel needs for 1000m and then multiply it by 7 (as gearbox sensor sends 7 impulses per wheel rotation). The tricky thing about using your custom K value is that after recoding using same coding as before (to recalculate checksum and remove DEF error) you are loosing your custom K value. For VMK501 clusters there is easy solution - you just need to set your dump to have 0 as last digit of cluster coding. For VMK503 clusters there should be a solution but if you set the dump to have 0 as last digit of coding the DEF error will not be cleared. Do not forget that speedometer scale/stepper motor settings are also covered by checksum protection."
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canigetawitness
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« Reply #6 on: August 10, 2015, 06:40:28 AM »

Thanks for the reply Adam.
Yes, I've read a few comments about how speedos are made to deliberately read a little higher than the actual speed. I posted on another forum and they said 3mph higher could just be the way it normally works. Just doesn't si right with me. Seems a significant different. Like it's almost dangerous(I know that makes no sense though).
I had trouble setting the k value to what it was meant to be. Would only accept a 0 which gave a wildly incorrect speedo reading. Then I repeated the adaptation, fisrt coding the hex values into the cluster's eeprom code and writing back. And that led to this latest situation. So maybe this is just normal. Maybe my old cluster did this too and I never noticed. Would probably explain all those irate people when Im doing 30 in aa 30 zone or 40 in a 40 zone!
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adam-
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« Reply #7 on: August 10, 2015, 07:12:33 AM »

If you can pull the EEPROM from the clocks, you can edit all of the values manually, no need for adaptations.

The K value is stored at - 0x150 [0x192] - K value stored as LoHi 16 bit number.  The two addresses are for different clocks.

Wouldn't be too hard to calculate, but it's never bothered me that much.  Just add a few mph to your current speed to adjust. Wink

I don't think they're irate because you're going too slowly; it's just a thing in the UK where it's compulsory to speed everywhere.

I've been overtaken a few times by doing the speed limit (30 in a 30).  Furthermore, it seems the done thing to do 40 in a 30, and then continue to do 40 in a 60.  Idiots.
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canigetawitness
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« Reply #8 on: August 10, 2015, 07:29:55 AM »

Ha ha ha that last bit made me laugh. Yes I have noticed these things too. Whenever I want to go at the speed  limit everyone demands that I go much faster, and if I'm in a rush, suddenly it's sunday driving everywhere. It's like The Truman Show or something.
Now what you wrote there is interesting. Maybe I have confused this K value with the distance impulse miltiplier in the cluster's softcoding, which by comparison I found to be at 00001C, 00001D, 00011C, 00011D, 00021C, 00021D. So that's the part I had to change manually.
So the K value is a separate deal to that? Sorry, learning as I go here.
So should I do anything with this K value or leave it alone?
I didn't quite understand the part about the 0 at the end of the softcoding. When mine was set to 0 it was way out(showing 20mph for 40mph), so maybe it was the other type of cluster they mentioned in that quote. I'm a bit lost with this I'm afraid.
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adam-
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« Reply #9 on: August 10, 2015, 08:04:59 AM »

I swear you're right, it's exactly the same in Glasgow!  That, and motorway etiquette is generally appalling.  Sitting in the right hand lane for no reason, when both two lanes are totally clear.  I find myself having to cut across three lanes to then over come all the way back across.  People are just clueless and it really annoys me.

Yes, I think you're right.  I've not changed mine because when I'm doing 30, people are sat up my chuff.  Do 60 and people fly past.  I know that I'm doing roughly the speed limit and I've not really thought about it.

I'm sure there's a method on how to calculate it, I'll have a Google when I get home for you.  Otherwise, you could load the EEPROM (pulled with vag commander 2.5 or similar) and edit the value.  Either increase 5% and see the effect, decrease 5% and see the effect.  Edit until you get it close; that's all I'd say! Smiley
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canigetawitness
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« Reply #10 on: August 10, 2015, 09:12:36 AM »

Exactly. That was always a bug bear motorway driving. When people stop driving by the rules of the motorway, the motorway doesn't function any more. I heard they were going to fine people for middle lane hogging and tail gaiting anyway. Long overdue. either they need to enforce motorway driving rules better or scrap it and introduce freeway driving rules. I prefer motorway rules though cos I dont think we have enough lanes for freeway driving to work.

Thanks a lot for the advice on the K value. That is a new one on me. I'll bear that in mind if I decide this 0-3 mph over is not liveable with. In the quoted text, it sounded like there's a complication when you rewrite it though and I couldn't quite follow that part. I'm a bit thick like that! But I'll cross that when I come to it I guess.
Thanks again Adam. Much appreciated.
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hytron
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« Reply #11 on: August 21, 2015, 10:57:30 PM »

OK it proved very difficult to do a test on the motorway - busy, people driving dangerously badly, Tom Tom just refusing to work. But I managed to work it through the lower ranges again anyway, and again afterwards. It's hard to know what to say about this. It seems to work through a range of 0 -3 mph from 0 to 60 but while it's ~1 difference at 10, maybe 2 at 20, then it seems to remain at about a 3 mph differnce from 30 to 60. Which doesn't make a fat lot of sense to me. Someone suggested an output test so will try that.
I'm also wondering from some of the other errors I've been getting if my ECU may need rebuilding. The root cause of all this was an immobiliser activated message that started right after I had a coolant leak and the mechanic fixed it. I don't know how but I think somehow, the ECU or leads going to may have got wet. I did a check of the leads going in a couple of times and looked tip top. Couldnt get the ECU out of its housing, then did and couldnt get it open without forcing it cos I didn't know if that could do damge or break an important seal or something. Guess it's time to force it though. But before I came across these error messages, elimination and googling had led me to believe it was bad soldering in the cluster, hence the replacement.

I am experiencing the same issue in my 2006 VW Jetta TDI. At about 60mph (GPS measured), the speedometer would indicate 65mph, so it is about 8% error. I have seen some talks about it and VW claims it is normal as they don't want to responsible for speeding tickets in case it showed less. This has been bothering me and I would like to know what to change in the instrument cluster for the gauge to show the correct speed. Are we talking about modifying the content of serial EEPROM 24C32 or something else?

Not sure if I got from this thread how to do this...

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hytron
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« Reply #12 on: August 21, 2015, 11:03:14 PM »

Just to add to my previous message...I have tested

2004 Acura TL - 70mph GPS - 70mph Speedo
2012 Chevy Cruze - 70mph GPS - 70mph Speedo

My both VWs 2003 Jetta and 2006 Jetta are showing the incorrect speed, or slightly higher speed. I would like them also to be exact.

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hopsis
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« Reply #13 on: August 22, 2015, 02:56:49 AM »

How about a lo-tech solution? I noticed the same "error" in my car. It isn't so much to do with how many mph or kph the the actual speed varies from the speed displayed. If You look at the speedometer, i bet You 9 times out of 10 the same difference is the distance the speedometer needle should be further. Sorry for the awdward way to explain this, english isn't my native language.

Anyway, if You look at Your speedo when doing 50 verified with GPS and look how far off the needle is from the actual speed, then raise the speed to 80 and look if the needle is still as far off You get what I'm talking about. Way I fixed it, was to take the front cover and speedo needle off, then take the car to 100kph (GPS) an plug the needle so that it points to the correct speed. Takes 10 minutes and now I have the speedo working right where it matters the most, I don't much care if there is now some error at 200kph.
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canigetawitness
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« Reply #14 on: August 22, 2015, 05:55:54 AM »

I am experiencing the same issue in my 2006 VW Jetta TDI. At about 60mph (GPS measured), the speedometer would indicate 65mph, so it is about 8% error. I have seen some talks about it and VW claims it is normal as they don't want to responsible for speeding tickets in case it showed less. This has been bothering me and I would like to know what to change in the instrument cluster for the gauge to show the correct speed. Are we talking about modifying the content of serial EEPROM 24C32 or something else?

Not sure if I got from this thread how to do this...


Hey Hytron,
I agree, I would prefer an accurate reading but a lot of people on forums(fora!?) claim that this higher reading is a deliberate safety measure in a lot of modern cars. And it may be that is just a European standard. I think I read that the rule allows for speedos to read higher up to (10% of your speed + 4kph) but they must always read higher. So my 2-3 mph at 30/40mph doesn't seem that high after all! I'm not the best at wading through lots of threads but I guess I read a fair amount on this one and it seems to me the general consensus is you either fiddle the Distance Impulse Multiplier to reflect the right speed, but then adverseley affect the odometer; or you just live with it reading high. But I'm not 100% about the Distance Impulse Multiplier affecting odometer - there was some debate about that and I'm just erring on the side of caution by assuming it does in my case.

I imagine you already know this but for anyone else who doesn't, the Distance Impulse Multiplier is set via the last(5th) digit of the Instruments softcoding(5 digit field that appears under "17 - Instruments" in VAG COM/VCDS). I can't tell you the precise technical definition but it's to do with how many times the tyres rotate over a given distance so obviously tyre size affects it. If you get tyres with a larger circumference, you're going to want to lower that number or your speedo.

The setting on my last cluster was 01414 where the 5th digit, 4, is the Distance Impulse Multiplier.

Setting the Distance Impulse Multiplier in VAG COM(VCDS) by changing the last digit of "17 Instruments" softcoding, you will have a set number of options available and I believe that varies for different models, but for my car there are be 4 values to choose from:

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

VCDS also says there's a 0 option which covers all eventualities by getting the impulses through the CAN. However I couldn't code my car to this value using VCDS. I tried hard coding it via other means but the speedo was way off.

These are the results I got from changing these values then testing the speed at 30-40 mph:
0 = get impulses through CAN - speedo reading 14-16 mph under actual speed
1 = 4345 impulses/km - speedo reading 3-4 mph under actual speed
2 = 3528 impulses/km - speedo reading 3-4 mph over actual speed
3 = 4134 impulses/km - speedo reading 1-2 mph under actual speed
4 = 3648 impulses/km - speedo reading 2-3mph over actual speed

It's a bad idea to have it reading under, so I went with 4 as it was the closest higher reading.

These options appear as a tooltip when you go into VCDS and click "17 Insturments > 07 Recode" (or "07 Coding" on more recent versions) and click into the softcoding field.

1) To change it via VCDS:
SELECT > 17 Instruments > 07 Recode
overwrite existing value with new value and save it. This should take effect without any kind of cluster reset. I think I just turned the ignition off then on again and it took effect.

2) to change it with an EEPROM editor, you'll need to know beyond any doubt which addesses correspond to your softcoding and change them all 100% accurately before writing the EEPROM back. I believe that if you make any errors there's a risk of bricking the cluster, though fortunately this didn't happen in my case. But you definitely want to make a backup of your cluster's EEPROM before attempting anything like this so, hopefully, you can restore it if it goes wrong.

So in mine I figured out by changing it in VCDS and comparing files, working out what the numbers were, that it was stored in 3 locations:
i) 00001c, 00001d
ii) 00011c, 00011d
iii) 00021c, 00021d

(remember that the above addresses will vary depending on what cluster you have so DO NOT go blindly trying to change them or you will wreck your cluster if it's the wrong locations)

The reason there's 2 addresses for each is there's 2 x 2 digit hexadecimal numbers making up the code. For some reason they are stored in reverse order so you take them, switch them round, then run them through a Hexadecimal > Decimal converter to work out the actual code or vice versa. Here's an example.
So each of those 3 locations above currently stores "86 05" in my case. So if I want to know the digital value that corresponds to, I swithc the numbers first, giving me "05 86", then I put them through the Hex> Dec converter (like this: http://www.rapidtables.com/convert/number/hex-to-decimal.htm) and it tells me "1414" which matches my cluster's softcoding.

To do this work on mine I used VAG EEPROM Programmer but there's other software that can do this like VAG K Commander. You also need a K-line OBD2 cable and a laptop to run VAG EEPROM Programmer from. Not unusual to need multiple attempts to read/write. The only thing I'd warn you is that sometimes, when I attempted to hard code the 0 value in or cod it back to 1,2 3,4 from the 0 value, it didn't always take and I had to do a new cluster adaptation to get it back to the other value range. SAo my advice to you would be to perhaps stiuck to VAG Com/VCDS and only enter what it allows you to in there.

3) I have read something about actually hard coding the impulse value in to make the speedo reflect the speed. But I was afraid this would throw the odometer out so I didn't go down that route. Plus the Hex addresses provided don't seem to hold that info in my case.

If there's any inaccuracies in the above info, I'm seriously just a begninner at this stuff so don't be too harsh!
« Last Edit: August 22, 2015, 01:35:30 PM by canigetawitness » Logged
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