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ballast
Member Since: 13 Apr 2007
Location: South Midlands
Posts: 177
  
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| Random one for the boffins |
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When I bought my current D3 a few years back, I bought it in the knowledge that it had had a replacement speedo during its life and that the mileage displayed on the new speedo was incorrect (i.e. lower than reality). I will at some point buy an IID and correct it, but just can't justify it at the moment.
Anyway, I was looking at the stored mileages in the Terrain Response ECU to see what the actual correct mileage of the vehicle is and I've done all that no problem.
My query is that the ECU's also store the mileage in what I assumed was Hex (as well as readable decimal in miles), but when I convert these values from Hex to decimal, they don't equal the stored decimal mileage.
The reason I was interested in the Hex values is that the ECU contains a Hex only value for 'distance travelled special programmes off' which isn't available in decimal miles, also (and finally), the Instrument ECU offers an Odometer value which also appears to be in Hex, but again when I convert it, is incorrect; I'm assuming this is the correct total mileage of the vehicle.
Can anyone shed any light?
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 14th Jan 2021 9:04 am |
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Bungle
Member Since: 07 Apr 2015
Location: Wanborough
Posts: 254
 
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Could it be one is in miles and the other in Kilometres? Just a thought......
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| 14th Jan 2021 9:50 am |
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ballast
Member Since: 13 Apr 2007
Location: South Midlands
Posts: 177
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Defo not KM. Example of one of the numbers is 0019C0 which should equate to 4096.08 miles....
But 0019C0 conversion from Hex to decimal doesn't work out.
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| 14th Jan 2021 10:07 am |
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McAdam
Member Since: 21 Nov 2020
Location: Canary Islands
Posts: 129
 
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AFAIK the actual mileage is not stored in the display cluster.
There is one central truth in the system (can remember in which ECU).
So changing the display cluster and mating it to the car should not have changed the mileage.
I looked into this when I bought my car, which is a LHD but left the factory with MPH clocks.
It is in my plans to convert the car to KM/H at some point. Pre-Production
D3 V8 #264
LHD '04 HSE
Living its life as a 50/50 On/Off road car exploring the Canary Islands
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| 14th Jan 2021 10:12 am |
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Flack
Member Since: 06 Sep 2006
Location: Preston Lancashire
Posts: 6232
 
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What tool are you using to read the mileage, from memory I think its the BCU and the PCM that has the correct mileage stored.
Unless the system has been re-synced it wont display the correct values.
Flack 
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| 14th Jan 2021 10:40 am |
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ballast
Member Since: 13 Apr 2007
Location: South Midlands
Posts: 177
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I used the Autel AP200 (discussed on a separate thread on here; I've got a Hawkeye too which correlates). I couldn't find anything stored in BCU relating to mileage and having done a few Google searches, it seems as though Terrain Response ECU, plus a separate EPROM store the master data re mileage. As noted previously, the Instrument Cluster ECU has an odometer value, seemingly in hex (04634C), but converting this to decimal doesn't work.
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| 14th Jan 2021 10:50 am |
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ballast
Member Since: 13 Apr 2007
Location: South Midlands
Posts: 177
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Sorry, meant to say, couldn't find anything mileage related in PCM either...
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| 14th Jan 2021 10:51 am |
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Rusty_US
Member Since: 18 Mar 2017
Location: Sourdeval, Manche
Posts: 34
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ballast wrote:Defo not KM. Example of one of the numbers is 0019C0 which should equate to 4096.08 miles....
But 0019C0 conversion from Hex to decimal doesn't work out.
Doesn't HEX 0019C0 become 6592, which if then converted to miles is 4096.08
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| 14th Jan 2021 11:08 am |
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ballast
Member Since: 13 Apr 2007
Location: South Midlands
Posts: 177
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this is where I'm being thick and I'm worried I'm going to display that right now..... how does 6592 convert to 4096.08 miles?
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| 14th Jan 2021 11:10 am |
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ballast
Member Since: 13 Apr 2007
Location: South Midlands
Posts: 177
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got it! and apologies to Bungle. The conversion is into KM!! of course..
thanks folks - at least I now know  
Hex to KM to miles....
Much happier now.
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| 14th Jan 2021 11:15 am |
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ballast
Member Since: 13 Apr 2007
Location: South Midlands
Posts: 177
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So, just because I've got nothing else to do, the output from the TR and Instrument Cluster ECU is interesting....
Unsurprisingly, the Instrument Cluster ECU is (nearly?) the same as the displayed mileage (but not quite!).
Displayed = 178722 miles. ECU = 04634C = 287564KM = 178683 miles (not sure why these aren't the same?)
Then on the TR ECU, there's a hex unit of 0637E8 against 'distance travelled with special programmes off' which is 407528KM which = 253226 miles (i.e. mode 1)
When I add the mileage of each of the Terrain Response modes, it comes to 257371 miles. I think this is the total mileage of the car.
It's done 4096 miles in mode 2 (snow/grass!!!).
Last edited by ballast on 14th Jan 2021 12:44 pm. Edited 2 times in total
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| 14th Jan 2021 11:29 am |
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ballast
Member Since: 13 Apr 2007
Location: South Midlands
Posts: 177
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And my final point on this 
as per McAdam's point, I'm surprised that the Instrument Cluster ECU doesn't just drag the correct (higher) mileage from the centrally held actual total mileage. This (I think) would imply that wherever that central source is has either (a) been deliberately changed or (b) corrupt the central source.
And the Terrain Response ECU doesn't pass information between it and other mileage data stores.
The MOT history would seem to support the mileage that I think it's actually at (i.e. roughly 257K)
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| 14th Jan 2021 11:36 am |
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