Introduction. One of the most important tasks when buying a used car is to verify the real mileage. In Europe — and especially in Germany — odometer tampering is a criminal offence, but unfortunately this does not mean it never happens. A lowered mileage allows dishonest sellers to ask for more money, because a car with “low km” is always easier to sell and usually more expensive.
So how can you find out whether the mileage on the dashboard is actually true? In this article we will look at modern methods, especially pre-purchase computer diagnostics, which helps to uncover odometer fraud even when the seller is trying to be clever. We will also briefly touch on why mileage is rolled back in the first place, what the legal consequences are in Germany and what other valuable information you can get from a professional diagnostic scan when inspecting a car.
Why mileage is manipulated and how often it happens
The motivation is simple: a car with lower displayed mileage can be sold faster and for more money. The price difference between a car with 150,000 km and the same model with “80,000 km” can be several thousand euros. That is what some sellers are aiming for. Despite rapid technical progress, odometer fraud remains a widespread phenomenon. When buying from a private person or small trader, you should always keep the possibility of manipulated mileage in mind.
Typical reasons for rolling back the odometer:
- ❗ Direct financial gain. Lower km = higher price, especially on popular and expensive models.
- ❗ Marketing trick. Psychologically a car with 100,000 km looks much more attractive than one with 250,000 km, even if the real technical condition is similar.
- ❗ Hiding excessive use. Ex-rental, taxi or company cars often cover huge distances in a short time. Before selling, the mileage is “rejuvenated” to hide the heavy use.
- ❗ Avoiding penalties in leasing. In some cases, people roll back the mileage before returning a leased vehicle to avoid surcharges for exceeded km limits.
From a legal perspective, odometer manipulation in Germany is classified as fraud and can be punished with fines and even prison sentences. For the buyer, discovering the fact of manipulation afterwards can be a strong basis for cancelling the contract or demanding compensation. Because of this, many fraudsters go to great lengths to cover their tracks — which is exactly why a thorough check is so important.
How to check if the mileage has been rolled back: role of computer diagnostics
There are several ways to estimate the real mileage of a car, but one of the most reliable is to read the data stored in its control units with a professional diagnostic tool. A modern car usually stores mileage not only in the odometer, but also in several other electronic modules. If someone has only changed the value displayed on the instrument cluster, original figures may still remain elsewhere.
Typical mileage sources inside the car
- 📜 Engine ECU. Many models record total mileage or engine hours in the main engine control unit.
- 📜 Automatic transmission (TCU). Gearbox control units often keep separate counters for km or hours.
- 📜 ABS/ESP module. The ABS or stability control module can store its own mileage information based on wheel speed signals.
- 📜 DPF control (diesels). For diesel engines, the DPF module may log distance travelled between regenerations and total distance.
- 📜 Key & instrument cluster. On some brands (e.g. BMW, Mercedes) the mileage is additionally written to the electronic key and several other places in the car.
A specialist connects a dealer-level scanner or advanced diagnostic tool to the OBD-II port and reads these values. If there is a clear difference between the dashboard reading and the mileage stored in the ECU or ABS, you can confidently talk about manipulation. Even if no mismatch is found, such a check is useful: it either confirms the seller’s honesty or reveals that something is wrong.
Why this approach works
True, some “professionals” in fraud now use expensive tools to adjust mileage in multiple modules at once. But the majority of rollbacks on the market are still done by amateurs or small traders who either don’t know about all the backup locations or don’t have the equipment to change them. They may forget to clear data in some modules, or not know how to access them safely.
- The instrument cluster is not the only place where mileage is stored.
- Error memories often contain “km stamps” from past events.
- Even if everything matches, you still get strong confirmation that the mileage is likely genuine.
Important: deep diagnostics requires professional equipment and know-how. Simple OBD adapters and smartphone apps usually cannot see all relevant modules and data.
What deep computer diagnostics can reveal about mileage
-
✔ Direct mileage values in modules.
Example: ECU shows 180,000 km, dashboard shows 120,000 km → clearly manipulated. The more modules confirm the higher value, the stronger your case. -
✔ Engine hours.
Some systems allow reading the engine run time in hours. Knowing typical average speed (for city cars often around 30–40 km/h), you can estimate the real distance travelled. If the odometer says 50,000 km but the engine has, say, 3,000 hours (which corresponds roughly to 90–120k km), something is off. -
✔ Error memories with km stamps.
When certain faults are stored, the system often logs the mileage at which they occurred. A diagnostic report might show, for example: “fault recorded at 210,000 km” while the current odometer shows 150,000 km. This is a very clear sign that the car once had a higher mileage than shown now. -
✔ Service history stored in control units.
Some brands keep information about past services directly in the ECU or service module: dates and mileage at which maintenance was performed. If the last service entry is at a higher value than the current odometer, the car has been “rejuvenated” at some point. -
✔ VIN consistency and module replacements.
By checking the VIN stored in different control units you can see whether they all belong to the same car. A “non-original” airbag or ABS module, for example, can hint at a serious accident and subsequent repairs — sometimes combined with mileage manipulation.
Ideally such diagnostics is done before you buy the car. In theory you can do it yourself, but in practice you need proper tools and experience. Simple OBD dongles provide only a very limited picture. A professional knows exactly where the relevant data is stored on a specific brand and model and how to read it without causing errors.
What to do if you suspect odometer fraud
Let’s say diagnostics has shown that the advertised mileage does not match the internal data and you now have good reason to believe the odometer was rolled back. How should you react?
It depends on the stage of the deal:
-
Before signing any contract:
The safest option is simply to walk away. At the very least you should negotiate a serious discount. Once a seller is caught lying, trust is gone — and in many cases mileage fraud goes hand in hand with other issues (overdue maintenance, hidden accident damage, ignoring warnings). If you still really like the car, involve an independent expert and reassess the price very carefully. -
After purchase:
In Germany, discovering odometer fraud can be a strong basis for revoking the contract and returning the car to the seller with a refund. Legally the vehicle was sold with false information. You will, however, need proof: diagnostic reports, expert opinions (Gutachter), old service records, external history reports (CarVertical etc.). In many cases, once the seller realises that you can prove fraud and are willing to escalate, they prefer an out-of-court settlement. -
Report the case.
Informing the police or relevant consumer organisations helps fight fraud on the market in general.
Of course, it is much better to detect such problems before you transfer any money. That is why we repeat: never rely on the odometer alone and do not let a “too good to be true” offer distract you from a proper technical check.
Other benefits of computer diagnostics before buying a car
Besides confirming the mileage, pre-purchase computer diagnostics in Germany can give you a very detailed picture of the car’s health.
📢 Engine parameters in real time
- Live data: fuel pressure, injection corrections (fuel trims), intake air values, coolant temperature, etc.
- Indirect indicators of compression and wear patterns visible to an experienced technician.
- Charging system and battery state of health under load.
📢 Automatic gearbox condition
- Error codes stored in the transmission control unit.
- Oil temperature history, clutch wear indicators (on some models), adaptation data.
- Signs of overheating or slipping that can predict expensive future repairs.
📢 Braking system & ABS/ESP
- Status of all ABS wheel speed sensors and the ESP unit.
- Differences in wheel speed that may hint at wrong tyre sizes or sensor faults.
- Airbag/occupant safety system: codes that can show previous deployments or module replacements.
📢 Climate control & comfort electronics
- Error codes for climate system flaps, compressor, low refrigerant pressure, etc.
- Electrical system data: alternator performance, battery voltage under different loads.
📢 Hybrids & electric vehicles
- State of health (SoH) of the high-voltage battery: remaining capacity, cell balance.
- Statistics about fast and slow charges, temperature extremes, power limitations.
- For EVs and plug-in hybrids this data is absolutely crucial, as the battery is one of the most expensive components in the vehicle.
📢 Chip tuning & software modifications
- On many cars the scanner can show whether the ECU software is original or has been modified.
- Chip tuning is not always bad, but it is important to know about it and understand how it was done.
📢 Remaining distance to next service
- Many vehicles store data about when the next service is due in km and/or days.
- If these values are illogical (for example, a “major service” was allegedly just done, but the system still insists on service soon), it is a good reason to ask the seller more questions.
As you can see, a comprehensive scanner check before buying a used car is extremely informative. Combined with a visual inspection and a proper test drive, it gives you a nearly complete picture of the technical condition — particularly important in Germany, where cars are full of electronics that can “tell their story” if you know how to listen.
Conclusions & how Sicher-Check helps
Computer diagnostics before buying a car in Germany is one of the most reliable ways to confirm the real mileage and assess the true condition of a vehicle.
Electronic diagnostics is a powerful tool in the hands of an experienced specialist. It helps to reveal rolled-back odometers, detect hidden defects and make sure you are buying a solid car rather than a “pig in a poke”. However, the data needs to be interpreted correctly — numbers alone are not enough.
If you are not deeply familiar with the technical side, the best solution is to involve a professional. The experts at Sicher-Check have extensive experience with pre-purchase inspections and full computer diagnostics of used cars in Germany. We read all available control units, analyse fault codes, check mileage traces and combine this with a full on-site inspection and test drive. In the end you receive a clear written report with our recommendation whether to buy the car or continue searching.
Our car buying support for Berlin / Germany includes not only finding suitable cars according to your criteria, but also checking history, technical condition and legal aspects. We can help you all the way — from the first contact with the seller to signing the contract.
Don’t let odometer fraud and hidden defects ruin your purchase. Get Sicher-Check on your side — and we will help you choose a reliable car with honest mileage and a transparent history.
Werbung / *Affiliate-Link
Links and banners marked with an asterisk (*) are affiliate links/banners. If you use such a link and subsequently request an offer, sign a contract or make a purchase, we receive a commission from the respective provider. For you, there are no disadvantages: the price and conditions remain the same.