Bosch, Continental, Delphi, Marelli, Denso, Keihin: who builds which ECU
The main engine control unit suppliers at a glance: who builds which families, which vehicles they're fitted to and why it matters for tuning.
October 26, 2026 by Leo Efimow
A car wears its brand's badge, but the engine control unit almost never comes from the car maker itself. It comes from a supplier, and which one carries more weight for tuning than the badge on the bonnet. A Peugeot can have a Bosch, a Continental or a Delphi ECU; a BMW a Bosch or a Siemens unit. This article gives you an overview of the main suppliers, their ECU families and the vehicles they're typically fitted to.
Why the ECU supplier matters
For tuning, the ECU's supplier determines three things:
- How the software is structured: Each supplier has its own concepts for organising torque, cylinder filling and protection functions.
- The access route: OBD, bench or opened housing: that depends on supplier, family and generation.
- Tool support: Some families are widely covered in the industry; with others, a lot depends on the exact variant and software version.
That's why our price depends on the ECU generation, not on the car brand.
The suppliers at a glance
| Supplier | Typical families | Typically fitted to |
|---|---|---|
| Bosch | EDC15/16/17, MD1 (diesel); ME7, MED9, MED17, ME17, MG1 (petrol) | VW, Audi, Seat, Skoda, BMW, Mercedes, Ford, Opel, Fiat, PSA, Hyundai/Kia |
| Siemens / Continental | SID80x, SID20x, SID30x (diesel); Simos, SIM, EMS (petrol); at BMW MS4x, MSV, MSD | PSA, Ford, Renault/Dacia/Nissan, Land Rover, Jaguar, VAG petrol engines, older BMW |
| Delphi | DDCR, DCM1.2, DCM3.x, DCM6.x, CRD3 | Renault/Dacia 1.5 dCi, PSA/Ford 2.0 HDi/TDCi, Hyundai/Kia, Opel, Mercedes OM651 |
| Magneti Marelli | Multijet diesel (MJD, MJ8, MJ9); IAW, 8GMF (petrol) | Fiat, Alfa Romeo, Lancia, Abarth, Opel/Suzuki 1.3 diesel, older small VAG petrol engines |
| Denso | diesel and petrol ECUs, some with Transtron | Toyota, Lexus, Mazda, Subaru, Isuzu, Jaguar/Land Rover 5.0 supercharged |
| Keihin | motorcycle and car engine management | KTM, Husqvarna, Husaberg; Honda |
There are further suppliers with a smaller share in Europe, such as Visteon on older Ford models, Sagem and Valeo at Renault, Mitsubishi Electric, Hitachi and Kefico on Japanese and Korean vehicles.
Bosch: the market leader
Bosch is by far the largest supplier of engine control units in Europe. Motronic for petrol and EDC for diesel engines shaped entire generations. The EDC17 controls a whole diesel generation from VAG through BMW to Mercedes, the MED17 the petrol direct-injection engines of the same era. The successors are called MD1 (diesel) and MG1 (petrol) and are much better protected against changes.
Details are in the articles on the Bosch EDC17 and the Bosch MED17. How to read the Bosch part numbers on the label is explained in Reading Bosch numbers.
Siemens, VDO, Continental
Behind the names Siemens, Siemens VDO and Continental stands the same line. The diesel units are called SID and are mainly found in PSA, Ford and Renault diesels. On VAG petrol engines the Simos is widespread, and at BMW many petrol ECUs of the E generation came from Siemens, for example the MS43 in the 330i (E46) with the M54 engine or the MSD80 in the 335i (E9x) with the N54. More in Siemens/Continental SID explained and in the company history Siemens, VDO, Continental, Vitesco.
Delphi: strong in diesel
In diesel, Delphi supplied not only ECUs but complete common-rail systems. The DCM family is found in the Renault 1.5 dCi, in PSA and Ford diesels, at Hyundai, Kia and Opel; the CRD3 in Mercedes diesels. The diesel business is now part of BorgWarner, but the Delphi name has stuck in workshops. In detail in Delphi DCM3 to DCM6.
Magneti Marelli: Italy's electronics
Magneti Marelli was founded in 1919 as a joint venture between Fiat and Ercole Marelli and was part of the Fiat group for a long time. In tuning you'll mainly meet Marelli ECUs on the 1.3 Multijet in Fiat, Alfa Romeo, Lancia, Opel and Suzuki, and on petrol engines with MultiAir and TwinAir. Older IAW units were also fitted to small VAG and PSA petrol engines. Since the 2019 combination with Calsonic Kansei, the company has operated as Marelli.
Denso: the Japanese line
Denso is closely tied to the Toyota group and supplies many Japanese manufacturers. Typical are Toyota and Lexus, Mazda with SkyActiv engines, Subaru boxers and the supercharged V8s from Jaguar and Land Rover. Denso ECUs follow their own concepts and are less widely documented in the industry than Bosch. More in Denso ECUs: why the Japanese do it differently.
Keihin: from carburettors to motorcycle electronics
In the car world Keihin is mainly known from Honda, but in our day-to-day work through motorcycles: the injection ECUs of KTM, Husqvarna and Husaberg come from Keihin. Since 2021 Keihin, together with Showa and Nissin Kogyo, has been part of Hitachi Astemo. How tuning works on the off-road bikes is described in KTM EXC tuning with Keihin; you can configure your bike in the motorcycle configurator.
One engine, several suppliers
An important practical point: the engine doesn't fix the ECU supplier. Car makers buy from several suppliers and switch over the production run. The Renault 1.5 dCi is the best-known example: depending on year and version, it's controlled by a Delphi, a Siemens/Continental or a Bosch unit. PSA diesels and Ford also switch between Bosch, Siemens/Continental and Delphi depending on engine and generation.
That's why we ask for the vehicle data before the appointment and ideally for a photo of the ECU label. How to find it is in Which ECU do I have?.
Common questions from the workshop
Is a Bosch ECU easier to tune than one from another supplier? Not easier, but often more widely covered. Bosch families are particularly well documented in the industry. With other suppliers more depends on the exact variant. A clean modification is possible on all common families.
How do I recognise the supplier without removing the unit? Via diagnostics: many scan tools show the ECU supplier or type designation. The part number also reveals the supplier if you know its format.
Does it make a price difference who built the ECU? Indirectly. Our price depends on the ECU generation and on whether the unit has to be opened for access. The configurator shows the price for your car.
Conclusion
Bosch, Siemens/Continental, Delphi, Marelli, Denso and Keihin cover most of the ECUs on Europe's roads. If you know the supplier and family of your ECU, you already know a lot about access and effort. We work on non-BMW vehicles on site in Stödtlen or by mail-in, at the same price and bookable online. The software change voids the type approval; the software is intended for motorsport use only (motorsport notice).