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Old 30th July 2007, 12:19   #1
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Question Digital odometers query

Mod Note : Please continue the discussion in this thread (How to detect *Odometer Fraud*). Thanks

Just a simple query.. How do the digital odometers present in all cars now a days retain data even when the battery terminal is disconnected? I understand that most accessories like car steroes and clocks etc have a power backup of their own. In case of odometers, how can this backup last for decates?? The odometer reading is a sensitive data.

Has anyone of you accidently got the odo reading reset ever?

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Old 30th July 2007, 13:40   #2
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No, they have their own backup power supply.

You can find some interesting discussion here (incl. a Peugeot which clocked up extra miles while standing still in garage )
Back Room: Digital vs Analog odo
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Old 30th July 2007, 16:57   #3
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I know that the analog odo's can be reset or turned back a couple of hundred or even thousand kms before the car is sold (some even do it ). Is this possible on the digital ones? or do we take it for granted that they are tamper proof?
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Old 30th July 2007, 17:10   #4
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Everything can be done.
And i know where in chennai.
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Old 30th July 2007, 18:14   #5
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I'm not sure, they use some 'software' to flash the Odometer reading.
BTW it's illegal to tamper either manual/digital odometer in US, is it the same in our country, is there a law? if it doesnot exist, i think they really need to bring in that...
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Old 30th July 2007, 18:24   #6
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Tampering with odometer reading is illegal everywhere in the world.

But it is always possible to manipulate with right equipments
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Old 30th July 2007, 18:50   #7
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akahsm, There is something called EPROM. Erasable Programmable Memory. It retains its setting even after you turn the power off. This is the same thing that's in your washing machine for it to know where it was before the power went off.

There is also flash memory of the sort used in USB thumbdrives.

I'm not exactly sure which of these technologies is used for odometers, but it's certainly possible to retain settings even after battery disconnect.

Hope this helps.
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Old 31st July 2007, 00:00   #8
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Its EEPROM(Electrically Erasable PROM). Atleast Ford uses this method for storing data.
There are kits available to set ODO to any value, but its illegal almost everywhere.
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Old 31st July 2007, 01:09   #9
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Quote:
Originally Posted by nitrous View Post
Everything can be done.
And i know where in chennai.

You wicked man !!!!
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Old 31st July 2007, 01:44   #10
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there is a process whereby the mileage
is "backed up" in another component in the car. The instrument cluster
sends a software message to the other component every 100 km's, so that
the back up data is never more than 100 km's different than the reading
on the dash.

Every time the car is started the 2 data files are checked (as is the
VIN which is also stored in the redundant location). If there is a
mismatch in the mileage greater than 200 km's, then an "error" is set in
memory in the instrument cluster. If there is a mismatch in the VIN,
the cluster sets the "tamper indicator" - a small red led next to the
tripmeter reading.

And, the mileage data stored in the backup location can only be
overwritten by a "higher" value.

I am not identifying the backup component on purpose.

If the odometer is reset to 0 then the instrument cluster will reset it
again to the mileage stored in the backup component the next time the
car is started. But, if the odometer is set to anything other than 0
then the only thing that happens is the error code being set ( as
mentioned earlier ).

In theory a device that can change the odometer reading could also find
and cancel any error code, but that code should be set again when the
car is started. Sooooo - if someone turns an odometer back fraudulently
there should always be a telltale error in the memory of the instrument
cluster.

I understand that if you need a new instrument cluster, it is delivered
from BMW with the VIN number assigned to it - for your car, and the
mileage set to 0. The unit then restores all other data from the back
up source as long as the VIN numbers validate. (other data includes all
SI information).

//SOURCE Rivernet//

hope this helps, but sadly it will be much easier on our indian cars!
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Old 31st July 2007, 01:45   #11
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guys check this out
their is a website with all the details
Digital Mileage Correction
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