How do people change the odometer reading?

Question

I am a fan of getting a steal deal out of used cars. But most dealers out there usually mess with the odometer reading. While there are multiple technical ways to determine the age and condition of a vehicle (most of which I am not aware of), the easiest way for every person is to cross check the odometer and service history of the vehicle.

The issue with service history is that most people don't tend to do their service at authorized service centers (at least in India) and that too not as per the norms set by company. So, there won't be any records maintained after the first few years. So, I guess most people inspect the places where such used car dealers make mistakes such as the wear on the pedals, seat cover condition, rust formation etc. But often I have heard that tampering with digital odometer is hard. At least harder than the analog ones. Based on that I have a few questions.

1. But how does the new odometer technology work?
2. Is odometer reading stored in instrument cluster memory? If so, is it programmable by third party people? Again, how easy is to change the readings on instrument cluster?
3. Additionally, does ECU store this information? If so, does ECU check the odometer reading on the instrument cluster against the value stored in ECU?
4. Finally, is it easy to tamper the odometer reading stored in ECU by third party people?

Answer 1

But how does the new odometer technology work?

Not sure what you're asking. Basically, you drive ... the vehicle recognizes how far you've driven ... it records the ticks and translates it to mileage and stores the information.

Is odometer reading stored in instrument cluster memory?

It is my understanding the odometer reading is stored in several places, such as the ECU, instrument cluster, and other places.

If so, is it programmable by third party people?

Yes, it can be.

Again, how easy is to change the readings on instrument cluster?

With the right equipment, it's very easy.

Additionally, does ECU store this information? If so, does ECU check the odometer reading on the instrument cluster against the value stored in ECU?

This type of information is the type which the vehicle manufacturer doesn't really publicize. People have reversed engineered it to understand how it works and how the information is stored. They then devise ways to put new values into the storage places so the dash shows a better for them (lower mileage) situation than is actual. I've heard rumor that some of the reprogrammers which can be obtained to change the odometer don't do it in all the places within the vehicle, so sooner or later the system catches up with the reading and will change the odometer to the correct mileage. Unfortunately, this is well after the vehicle has been sold and is out and on its way. IOW: Buyer be ware.

Finally, is it easy to tamper the odometer reading stored in ECU by third party people?

I think your other question is pretty much the same as this, so I'll answer it the same: With the right tools, it's very easy.