How Does A Digital Odometer Work? (Explained For Beginners)

We cannot overstate how important an odometer is for your car. While most people think that odometers are only for prospective car buyers, they are also important for car owners because it tells them certain things like if it’s time for them to have their car maintained.

In that regard, it is also equally important for you to know how a digital odometer works in this day and age where an odometer can easily be tampered with.

So, how does a digital odometer work?

Digital odometers work by making use of magnetic or optical sensors that count the rotations made by a toothed wheel, which is connected to the car’s tires. The sensors will send pulse signals to the engine control unit, which uses an algorithm to calculate the distance traveled by the car based on the pulses.


We are now in a digital world where a lot of things are controlled digitally as most of the different tools and instruments we use on a daily basis have disregarded classic mechanisms.

As such, the odometer or the entire instrument cluster, for that matter, has become digitized as well, which makes it more accurate and long-lasting than its analog counterpart.

So, let us get to know more about the digital odometer and how it works.


How does a digital odometer work?

The odometer is one of the most useful instruments found on your instrument cluster because it tells you your car’s mileage or the total distance it has traveled since the first day it started moving.

This instrument is quite useful for those who want to buy or sell used cars because the odometer shows you how often the car has been used or how far it has been driven. 

That said, there are laws that are against odometer tampering as analog or mechanical odometers have become quite easy to tamper with in the old days where odometers were controlled mechanically.

That’s because mechanical odometers were controlled by simple mechanisms such as cables and gears that will turn the odometer based on how far the car has traveled.

Such a mechanism was simple enough but it was quite easy for people to alter and tamper with without a trace.

However, we now live in a day and age where a lot of the things we use are controlled digitally.

Gone are the days where we often relied on mechanical and analog tools, devices, and instruments that may not be as accurate as their digital counterparts.

In that case, even the instrument clusters on our cars are designed to fit the modern age because they are controlled digitally or electronically without relying on classic analog mechanisms.

But how does a digital odometer work if it no longer follows the same kind of mechanism that the older odometers use?

Well, for starters, you have to understand that the basic principles are still the same but digital odometers have made them simpler and more accurate.

In case you didn’t know, older odometers were basically controlled by a cable that attached the input shaft on the instrument cluster to an output shaft in the car’s transmission.

Every time the car’s tires turn or move, the output shaft prompts the cable to spin accordingly as the input shaft drives the different gear that will allow the odometer on the instrument cluster to move depending on rotations made by the car’s tires.

Quite simply, the odometer relies on the movement of the tires and is even calibrated to calculate the distance traveled by the car based on the size of the tires and the rotations they have made.

So, in the case of a digital odometer, the basic premise is still largely the same in the sense that it relies on the movement or rotations made by the tires and on the size of the tires themselves.

However, the difference is in how the rotations on the tires are being tracked.

Instead of making use of cables and gears, a digital odometer makes use of a magnetic or optical sensor found in the transmission.

There is a toothed wheel that moves or spins accordingly as the tires move as well. Meanwhile, the sensor keeps track of the movements of the toothed wheel and records them as pulses.

After that, the magnetic or optical sensor will send these pulses over to the engine control unit or ECU found in your car’s instrument cluster. Think of the engine control unit as the car’s main computer, which houses all of the data pertinent to your instrument cluster.

From there, the ECU will be the one to send the pulses to the digital odometer, which will now show your car’s mileage based on these pulses.

You can think of each pulse as one full rotation made by the car’s tires.

The odometer would then calculate the distance based on these pulses and on the size of the car’s tires so that it can have a more accurate estimation of how far the car has driven.

In a sense, digital odometers still rely on the rotations made by the tires and on the size of the tires themselves but now make use of a more digitized and advanced way of recording and calculating the distance traveled by car.

How do you read a digital odometer?

If you want to read a digital odometer, it is quite easy to the point that all you have to do is to look for your odometer on the instrument cluster.

The digital odometer will flash numbers on a digitized screen.

And these numbers should represent the car’s total mileage or kilometrage depending on the unit of measurement that is used by your car.

In that case, because digital odometers make use of a digital screen to flash your car’s mileage, the mechanical or analog way of using gears has now become obsolete. This makes it difficult to tamper with the odometer because of how you cannot just roll the gears back to show a lower mileage on the car’s odometer.

Can digital odometers be rolled back?

Now that we have established how a digital odometer works and how it is much more difficult to tamper with compared to an analog odometer, is it still possible for you to roll back your digital odometer?

Well, the thing you need to know is that no odometer is completely tamper-proof in the sense that there are still mechanisms and tools that are made and sold to actually roll back or stop your odometer.

Such tools are called odometer correction tools, which can either roll your odometer back or stop it from moving.

Odometer correction tools have their uses and are not made to be used to commit fraudulent acts. Instead, they are often used to actually correct an odometer such as when the car’s tires have been changed and that they come in a different size or when you have to actually stop the odometer in case all you need to do is to test-drive the car.

In such cases, it is perfectly fine for you to roll back or stop your odometer using odometer correction tools because of the very reason that you are not using the tools to commit fraud.

Some car repair shops actually have these tools but it can be pretty difficult to get them yourself because not a lot of online stores tend to sell them. That’s why they are usually only sold to repair or service centers that are there to make sure that your odometer is showing an accurate reading (e.g Odometer going too fast).

Of course, even if the digital odometer has been tampered with using an odometer correction tool, the thing you have to know is that the correct reading is still stored in the car’s ECU because it still keeps a record of the pulses recorded by the magnetic or optical sensor.

Car servicing shops usually have tools or devices that they can use to tell the car’s correct mileage by making use of the pulses in the ECU.

Can you stop a digital odometer?

As mentioned, there are some ways for you to stop a digital odometer or if the odometer is broken.

While rare, mileage stopper tools are actually being sold independently by certain websites.

And these mileage stoppers are usually considered to be more ethical than odometer rollback tools because of how they only serve to stop the car’s mileage whenever you have a good reason to do so.

One of the acceptable reasons for you to stop a digital odometer is when you are only test-driving the car because it doesn’t really “count” as actually driving the car.

In such a case, it is fine for you to use the mileage stopper to stop your odometer from counting your car’s mileage.

However, keep in mind that it is illegal for you to stop your car’s mileage whenever you are driving on an actual road.

You should only stop the digital odometer from running whenever you are test-driving the car or if you have a very specific and acceptable reason for doing so.

Otherwise, you shouldn’t even stop the digital odometer from keeping track of your car’s mileage.


How Odometers Work