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I read that the PCM tracks mileage for it's own purpose and BCM tracks and stores it for instrument cluster module to display it. So, when someone does an odometer/mileage correction, does it change the mileage value stored in the PCM or BCM or both?

  • So, who is the someone who changes the mileage - AFAIK it cannot be changed - if you have a replacement odometer at 75k then it starts from 0 again and people have to rely on a note made / log book entry etc – Solar Mike Jul 2 '18 at 8:25
  • There are scantools where you can change the odometer value to the desired value. It's a fraud. But I am wondering about which module's data changes – Soumya Sen Jul 2 '18 at 8:38
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    Any evidence of which scanner? As even the expensive garage ones don't have that function... Or does "I read " mean it was on *bay for a price and is a waste of money??? – Solar Mike Jul 2 '18 at 8:42
  • @SolarMike - Look here, here, here, and many, many more. Odometer fraud is real and happens all the time, even on new cars it's possible. There are tools available to make it happen, all you have to do is look for them. – Pᴀᴜʟsᴛᴇʀ2 Jul 2 '18 at 15:06
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    @SolarMike - I know newer cars store the odometer reading in more than one place (beyond the cluster and BCM). The crazy thing is (I understand) is if all of the stored places aren't changed at once, it can reset after a period of time ... great fun. – Pᴀᴜʟsᴛᴇʀ2 Jul 2 '18 at 15:44
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Millage correction is possible on ALL vehicles and it does have its legal uses.

Peugeot/Citroen suffer from a bug where the BSI gets corrupt and the millage changes to a random value, Landrover 2005/07 to around 2014 also had a issue where if a instrument cluster was incorrectly programmed it would put 99999 miles on the clock.

Then there is obviously the cases where you need to program a second had instrument cluster or other module which contains millage data.

So now we get to the question, Which module gets changed?

Every manufacture is different.

Most VAG & Landrover vehicles it is only contained in the Instrument Cluster

PSA is contained in the BSI and the Instrument Cluster

Newer Mercedes have it stored in the ABS ecu and Instrument Cluster

I'll update the list when I have more time

When it comes to tools which change the millage there is not a single tool which will do every vehicle. The tools which cost a few thousand (and their clones found on auction sites) are never worth the money, the best option is to buy a decent universal programmer and take the small amount of extra time to disassembly the required module and hook up to the necessary memory IC directly.

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