BMW MEVD17.4.2 ECU Files: Original, Immo/CAS Alignment and What Each File Does

The Bosch MEVD17.4.2 is the DME (engine ECU) of the BMW 1 Series F20 116i/118i (N13), the F30 320i/328i (N20) and the N55 six-cylinder in many F-series cars. It is a TriCore ECU with a hardware ISN, a tuning-protection layer and a tight link to the CAS/FEM body computer. “MEVD17.4.2 file” can mean four different things — this guide sorts them out.

The four file types

• Original file — a clean read of the full flash for a given hardware/software number. Used to recover a bricked DME or to return a tuned car to stock.
• Virgin / immo reset — the ISN pairing is cleared so a used DME can be aligned with the car’s CAS/FEM.
• Immo off — the DME no longer checks the ISN handshake. Only for cars with a dead CAS, race use or engine swaps.
• Tuning (Stage 1) — modified maps; requires a tuning-protection patch on this DME family.

ISN and CAS alignment

Every MEVD17 DME stores an ISN (individual serial number) which must match the ISN in the CAS3/CAS3+/FEM. When a used DME is fitted, the correct workshop path is to read the DME ISN and write it into the CAS (or read the CAS ISN and write it into the DME) with a tool such as Autohex, Yanhua ACDP or AVDI. A virgin file is useful when the DME comes locked from a donor with an unknown ISN; an immo off file is the fallback when no key data survives.

Reading and writing

OBD flashing is possible with tools that handle the MEVD17.4.2 protocol, but on protected software the full read requires bench or boot mode. Flex, KTAG and New Trasdata support the MEVD17.4.2 in bench/boot with the TC1797 processor. A boot read gives you the full flash plus the internal EEPROM that holds the ISN.

1. Read the full DME in bench/boot and save it — this is your recovery file.
2. Note the hardware number (Bosch 0 261 S1x xxx) and the BMW part number (8 6xx xxx) from the read or the label.
3. Write only files made for the same hardware and software version.
4. After writing, cycle the ignition and run a short adaptation drive.

Typical problems and fixes

• Car starts and dies after 2 seconds — ISN mismatch; align DME and CAS or use a virgin file plus alignment.
• DME no longer answers after a failed OBD flash — recover in boot mode with the original file.
• EWS/CAS fault codes after immo off — expected; the body computer still reports the missing handshake.

Getting the right file

Browse MEVD17.4.2 files and the wider BMW catalogue, matched by Bosch and BMW part numbers. Original reads for a specific software index can be prepared on request through the file request form.