Where is the vehicle's mileage stored?

Perhaps I missed it in the previous thread about the gentleman who had his odometer suddenly drop 100k miles when he disconnected and then reconnected his battery, but is there an official answer to whether the ecm stores the mileage along with the cluster. If not, then HOW did his mileage change after he reconnected the battery? I've been trying to figure out a solid answer to this question for a while now.

I've got a very low mileage tacoma (48k miles) that I've always been just a tiny bit suspicious about (probably just paranoid). The only records my truck came with were inspection printouts for every year since new. They all list the mileage. Each year the mileage increases between 1k and 2k. I've always wondered if the dude just disconnected the odometer for a majority of the year then reconnected it for 1k miles or so and then had it inspected as not to raise any eyebrows.

If the mileage were stored on the ecm, I should be able to check it against what the cluster reads.

 

Generally it is stored in the gauge cluster, When I swapped out my 99 cluster for an 04, I had to swap the odometer as well to maintain the correct mileage.

 

Right.
That's what I've always thought, but how did the odometer change back to correct mileage for the guy who disconnected his battery?

 

I found an article that might be interesting. Not saying it applies, but still quite interesting what people can do.

 

That is a very interesting question, one I have been pondering myself.

I understand the basics of how a digital odometer works, and how you could "modify" its reading. Where I am lost, is how those changes wouldn't be permanent and would be reset with the battery being disconnected. That perplexes me.

 

Could be possible. The chip stores the mileage in few places. If "hacker" reprogrammed the chip changing the reading only in one place, not all of them, the odometer might get into "recovery mode" after the power was restored and copy the reading stored in not altered place, which would be original mileage.

 

So do you know for sure that the mileage is stored in multiple places? These trucks age so well, it's really hard to tell if a truck has 100k miles or 250k miles. My mother's 03 4runner ran like the day she drove it off the lot---and it had about 270k miles on it when she traded it. Scary.

 

Yep, hard to tell, they are aging very slowly. Now my odometer shows a bit over 318k, but people don't know it is miles - they think km. But it is over half million km.

I watched this video
https://www.youtube.com/watch?v=uq6SlyVE4zQ

 

I'm 99% sure mileage is stored in the cluster only for our trucks. I've swapped ECU's a bunch of times and use a whole bunch of different scan tools and never once seen mileage stored in the engine ecu.

 

I have also replaced my ecu. Mileage did not change.

 

I had 289,000 miles on my truck when the cluster went out. I bought a used cluster with an odometer online and installed it now my truck says 260,000.

 

As for how the milage changed after connecting a battery, I'm betting either that person, or who ever had the vehicle before him was playing fast and free with hacking the mileage and just didn't get to everywhere the data is stored (that's on purpose - to prevent hacking). It's nearly impossible for just the *one* bit of code that holds the mileage to go wonky when nothing else goes wonky too - unless it's being hacked. I smell fish there...

It's more plausible the previous owner of your truck just didn't drive it very much. That seems like a LOT of work, and you'd need to be consistent *every time* you had it inspected. That's a lot of work. It's like the whole fake moon landing thing - where it would actually just be easier to build a rocket and go to the moon instead of creating such an elaborate fake.

What you SHOULD be suspect of, is when you have a series of inspections, that are increasing in mileage, then all of a sudden the mileage drops by 100k near the end.

 

are the non-digital odometers easy to tamper?

 

uhm, not 'hard'.
patience more than skill. That's why it used to be common.