How to find the HW and SW number of your ECU

To find an original file you need the numbers that identify your ECU's software, not just the make and model of the car. Two numbers do most of the work: the hardware number (HW) and the software number (SW). This guide shows where to find them for the most common ECU makers, and how to use them in a search.

HW, SW and calibration: what each number means

HW number — the part number of the physical control unit: housing, circuit board, processor, connector. One HW number is usually used with many software versions.
SW number — identifies the software inside the ECU. This is the number that decides which original file matches.
Calibration ID / SW upgrade — some manufacturers identify the dataset or a later update separately. Where it is listed, the file page shows it as "Calibration" or "SW upgrade".

On top of that there are usually two part numbers on the unit: the vehicle manufacturer's number (for example a Volkswagen-group number such as 03L906018 followed by suffix letters) and the ECU maker's own number. Either can appear as the HW number, depending on the make.

Three places to look

1. The label on the ECU

The sticker or laser marking on the housing shows the ECU maker's part number, usually the vehicle manufacturer's part number, and often a software or dataset number. It is the quickest source, but it has a catch: the label shows what was fitted at the factory. If the ECU was updated at a dealer later, the software inside no longer matches what the label says. Treat the label as a starting point, not as proof.

2. Diagnostic identification

A diagnostic tool connected to the OBD socket can ask the ECU to identify itself. Depending on the make and the tool you see part numbers, hardware and software versions and — on vehicles with OBD-II / EOBD — the calibration ID (CAL ID) and calibration verification number (CVN) that emissions diagnostics require. This reports the software that is actually running, so after updates it is more reliable than the label.

3. The read itself

If you already have a read of the ECU, the numbers are inside it. Most reading tools display the identification when they connect or after the read. WinOLS shows it in the project's properties and in the ECU's identification strings, and in any hex editor you can search the text view for a known part of the number.

Bosch

Bosch engine ECUs — EDC diesel units, ME/MED/MEVD petrol units and their successors — carry a ten-digit Bosch part number on the label. Petrol units usually start with 0 261, diesel units with 0 281. The vehicle manufacturer's part number is normally printed next to it.

The Bosch software number is most often a ten-digit number beginning with 1037; newer units also use a format that begins with 10SW. It is not always printed on the label, but reading tools report it and it is present in the read.

On our file pages, Bosch HW numbers are usually the 0 261… / 0 281… number or the vehicle maker's part number, and SW numbers the 1037… or 10SW… number. For a closer look at Bosch's best-known diesel family, see Bosch EDC17 explained.

Denso

For Toyota and Lexus, the label shows a Toyota part number of the form 89661-xxxxx or 89663-xxxxx and a separate Denso number. The software actually running is identified by Toyota's calibration ID, which a diagnostic tool reads out. In our archive most Toyota and Lexus files are listed with an 89663- software number plus the calibration ID. The numbering is explained in detail in Toyota and Lexus Denso ECU numbers.

Denso units for other makes — Mazda, Mitsubishi, Subaru, Nissan, Volvo and others — follow each vehicle manufacturer's numbering, with the Denso part number alongside. Some Denso numbers are so characteristic that our catalogue names ECU types after them, for example MB279700 units used by Volvo, Land Rover and Jaguar.

Continental and Siemens VDO

Continental took over Siemens VDO in 2007, so units of the same families appear under both names: SID diesel ECUs, SIMOS petrol ECUs, PCR units and others. The label carries a Continental or Siemens part number — often beginning with 5W or A2C — next to the vehicle manufacturer's number.

Which number we list as HW and SW depends on the make. Ford-fitted units, such as many SID20x and SID21x diesel ECUs, are usually listed with Ford part numbers (prefix – base – suffix; the base of an engine ECU is 12A650). Volkswagen-group units are listed with VAG part numbers.

Delphi

Delphi diesel ECUs of the DCM family (DCM3.2, DCM3.4, DCM3.5, DCM3.7, DCM6.2, DCM7.1 and others) carry the vehicle manufacturer's part number and a Delphi number. The software identification is reported over diagnostics and is present in the read.

Here, too, the vehicle maker's numbering usually decides what you search for. Mercedes-Benz units for the OM651 engine, for example, carry Mercedes part numbers that begin with 651, and that is how many of them are listed in our archive.

Searching with the numbers

Start with the SW number. If nothing matches, search the HW number and compare the SW numbers of the results.
Try different spellings. Search with and without spaces and dashes, or only the distinctive part of the number.
Narrow the field. The search box can look in "HW number" or "SW number" only. The Manual search tab of the search window lets you pick make, model, engine and ECU type, and add numbers on top. To browse instead, open your vehicle make or ECU type.
Mind the suffix. 03L906018 with two different suffix letters can be two different software versions.
Browse when you only know the car. Open your make and model, or your ECU type, and use your browser's find function (Ctrl+F) to look for your number on the list.

Several files with your HW number?That is normal: one hardware part number usually runs many software versions. The SW number or calibration ID decides which one is yours.

If you are still unsure, go through how to check you have the right original before you buy. All sales are final, so a minute spent comparing numbers is well spent.