In short
On a Mercedes-Benz, the remap is done on the engine ECU of each CDI or petrol engine, which depending on the generation is a Delphi or a Bosch, and on Sprinter and Vito vans it is usually geared towards low-down torque and working under load rather than peak power. Many automatic Mercedes have the 7G-Tronic or 9G-Tronic gearbox, with the transmission control unit inside the gearbox itself. The make also has very characteristic starting faults, such as the electronic steering lock. ECU remapping from from €200 + VAT (€242 including VAT), at our workshop in Alcalá de Henares or as a mobile service within the Community of Madrid.
Work van or car: two different goals
A Sprinter delivery van, an installer's Vito or a C-Class may share an engine, but they're not used the same way. With a car, people who remap usually want sharper throttle response. With a van, what matters is something else: climbing a mountain pass fully loaded without dropping two gears, not having your foot to the floor all the time and keeping fuel consumption under control. That's why on a work van we usually suggest an adjustment geared towards low-rev torque and working under load, which is what we explain in Eco remapping, rather than a file designed for a sports car.
If you have several vans, also see fleets: we plan the work so they're not all off the road at once.
The engines we see most and their ECUs
| Engine | Where you'll find it | Usual ECU |
|---|---|---|
| OM651 (four-cylinder diesel) | Sprinter, Vito, C-Class, E-Class and many more | Delphi on many versions; Bosch on others |
| OM642 (V6 diesel) | Sprinter, Vito, E-Class and large SUVs | Bosch EDC17 |
| OM654 (four-cylinder diesel) | Cars and vans from the middle of the last decade | Bosch MD1 |
| Renault-sourced diesels | A-Class, B-Class, Citan and some C-Class versions | Those of their Renault engine (see Renault and Dacia) |
| M270, M274 and later petrol engines | A, C, E-Class, GLA, GLC… | Bosch MED17; Bosch MG1 on the most recent |
The Delphi ECU on the OM651 is a quirk of the make: it isn't a Bosch like most German diesels, it's handled with a different method and some versions have to be removed. On the recent Bosch MD1 and MG1, as with other makes, the memory is protected and the work has to be done on the bench or by opening the unit.
7G-Tronic and 9G-Tronic: the control unit is inside the gearbox
On other makes, the transmission control unit is a separate box. On Mercedes' latest generations of automatics, the 7G-Tronic (seven speeds) and the 9G-Tronic (nine), the control electronics are built into the gearbox, next to the valve body. That has two practical consequences:
- To read or adjust it you don't look for it in the engine bay: the work is done through the gearbox itself, and if it has to be replaced, the gearbox sump has to come off.
- When it fails, the symptoms look mechanical (the gearbox sticks in one gear, goes into limp mode, changes gear with a jolt), but the cause is usually electronic. On the 7G-Tronic it's a well-known fault.
A new or second-hand transmission control unit needs to be programmed and adapted to that car. We cover it in automatic gearboxes and, if it's a replacement, in ECU cloning.
Why a Mercedes won't start even though the battery is fine
Mercedes uses a starting system with several parts that recognise one another: the key, the electronic ignition switch (EIS or EZS, where the key goes in) and, on many models from a few years ago, an electronic steering lock (ESL). When one of them fails or loses synchronisation, the car won't let the key turn, won't unlock the steering wheel or won't crank, even though everything else works.
The electronic steering lock is a typical fault on C-Class and E-Class generations from a few years ago. It's diagnosed by reading the ignition module and, depending on the case, the part is replaced and adapted or the problem is solved with one of our no-start solutions.
As for keys, the make has been locking down its system with each generation. On the most recent models, new keys can generally only be obtained through Mercedes. Before you pay anything, we'll tell you whether there's an alternative for your car. More detail in keys.
What we check first on a Mercedes
- Injectors: on high-mileage diesels, each injector's correction values tell us whether any of them is working outside the normal range.
- Timing: on some diesels, the chain is something we check if there's noise when cold.
- AdBlue on Euro 6 vans: warnings from the system, the NOx sensor or the tank heater. If there's a fault, it's repaired first: we only do deletes for motorsport or off-road use.
- Automatic gearbox: oil, harsh gear changes and codes from the internal electronics.
- Weight and use: on vans, the usual load and whether it tows a trailer, because that changes the approach to the file.
With all that, we'll tell you whether it's worth going ahead. The legal side, which is the same for every make, is in legality, ITV and insurance.
Tell us the model, engine and year and, if it's a van, what you use it for and how much load it carries. We'll tell you what makes sense to do and the price.
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