ECU Guides

How to Read Your ECU Label: Hardware Number, Software Number and Part Number Explained

21 September 2026 3 min read

Nine out of ten “the file does not work” cases come down to one thing: the file was made for a different software version. Every listing in our shop is tied to a hardware number and a software number, and the only way to buy the right one is to read them correctly from your ECU. This guide shows where they are on each manufacturer’s label and what each number means.

The three numbers

  • Hardware number identifies the physical ECU board. It is the supplier’s number (Bosch 0281 xxxxxx / 0261 Sxxxxx, Continental 5WPxxxxx / A2C, Delphi 28xxxxxx, Denso 275xxx / MB275xxx, Marelli IAWxxx / MJDxxx).
  • Manufacturer part number is the car maker’s number for the unit (VAG 03L906022AC, BMW 8xxxxxx, Hyundai 39110-xxxxx, Toyota 89661-xxxxx, PSA 96xxxxxx, Fiat 55xxxxxx).
  • Software number / version identifies the calibration inside. On VAG it is the four digits after the part number (e.g. 03L906022AC 3479); on Bosch labels it may be a 1037xxxxxx number; on Hyundai a suffix on the part number; on Toyota part of the 89661 number.

Bosch labels

Typical layout: line 1 Bosch hardware number (0281 016 xxx), line 2 manufacturer part number, line 3 software identifier (1037 5xxxxx) and a hardware index. Our titles for Bosch units follow “brand model ECU part number version software number”, for example “VW PASSAT MED17 03C906021P 6586 1037539340 DUMP”. Match at least the part number and the four-digit version.

Continental / Siemens

Look for the SW and HW lines printed directly on the label (SW: 5WP4xxxx, HW: 5WPxxxxx) plus the manufacturer number. SID and SIM units (SID807EVO, SID208, SIM2K-241) often show the software version only in the diagnostic identification, so read it with a tool.

Delphi, Denso, Marelli

  • Delphi (DCM3.x, DCM6.x): Delphi number 28xxxxxx plus the car maker’s number; the version is in the identification.
  • Denso: Toyota number 89661-xxxxx / 89663-xxxxx and Denso number 275036-xxxx; the Toyota number is the one to match.
  • Marelli (MJD 6F3, IAW 5SF, 8GMK): hardware and software codes on the label (HW xxx, SW xxx) plus the Fiat/PSA number.

Reading the numbers with a tool

If the label is unreadable, any diagnostic tool shows the control unit identification: part number, software version, coding. Flashing tools show the same data before reading. Bench tools such as KTAG and PCM Flash also display the identification found in the flash, which is the most reliable source because a replaced ECU may carry a label from another car.

Matching to a product

  1. Search the shop for the manufacturer part number (for example 03L906022AC).
  2. Among the results, pick the software version that matches yours.
  3. Check that the category is what you need: original, immo off, virgin, DPF off, stage 1.
  4. If the version is missing, do not buy the nearest one. Send the numbers or a label photo via the file request form.

Why the version matters

Two ECUs with the same hardware can carry calibrations for different engine codes, gearbox types, emission standards or markets. A file from another version can start the engine badly, trigger limp mode, or brick the unit on families with checksum and signature checks. Our checksum guide explains the mechanism.

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