ECU Guides

VW and Audi MED17 Immo Off: MED17.5.5, MED17.1.1, MED17.5.2 and MED17.1 Guide

30 October 2026 2 min read

Bosch MED17 is the engine ECU family behind almost every TSI and TFSI petrol engine from 2007 onwards: 1.2, 1.4, 1.8 and 2.0 litre units in Volkswagen, Audi, Skoda and Seat. Their immobilizer is tied to the cluster or the gateway, so a used ECU, a failed cluster or an engine swap ends with “cranks, no start”. This guide explains the VAG immobilizer generations and how MED17 immo off, virgin and original files are used.

MED17 variants and engines

  • MED17.5.5: 1.2 TSI, 1.4 TSI (CAXA, CAVC, CAVD) in Golf VI, Polo, Octavia, Ibiza.
  • MED17.5.2: 1.4 TSI and 2.0 TSI in Golf VI, Passat, Q3, Tiguan.
  • MED17.1.1 and MED17.1: 1.8 and 2.0 TFSI (CDNC, CDAA, CAEB) in A4, A5, Q5, Passat.
  • MED17.5.21 and MED17.5.25: 1.4/1.8/2.0 TSI on the MQB platform (Golf VII, Octavia III, Leon III).
  • MED17.5.1 and MED17.5.20: 1.4 TSI twincharger and later EA211 units.

VAG immobilizer generations

Immo 4 (PQ35/PQ46, 2004 to ~2013): the instrument cluster is the immobilizer master, storing the key data and the component security bytes; the ECU holds a copy and both must match. Immo 5 (MQB, MLB Evo, ~2013 onwards): the data is spread across the cluster, the gateway and the ECU with component protection on top, and adaptation requires online dealer access. In both generations the ECU refuses injection when the exchange fails, giving codes like 01176, 01179, 03303 or “immobilizer active” in the cluster.

Options for a non-starting car

  • Immo off file: the ECU no longer checks the immobilizer; the engine starts with any key. Best for engine swaps, dead clusters, exports and used ECUs where coding is not possible.
  • Virgin file: the ECU is reset and then adapted to the cluster with ODIS/VCDS (Immo 4) or online with ODIS (Immo 5). Keeps the factory security.
  • Cloning: copy the EEPROM of the original ECU into the donor if the original still reads.

Reading and writing MED17

MED17 runs on Infineon Tricore TC1766/TC1767/TC1793/TC1797. Early versions accept OBD with KESS V2; most units are read on the bench with PCM Flash, KTAG or FLEX, and locked units in boot mode. The immo data lives in the internal EEPROM (dataflash), so immo off and virgin work require the full read, not just the calibration.

Procedure

  1. Note the VAG part number (03C906xxx, 06J906xxx, 8K0907xxx, 04E906xxx) and the software version from the label or the tool.
  2. Read the full ECU and keep the file.
  3. Write the immo off or virgin file for the same part number and version.
  4. Clear codes; on Immo 4 cars the cluster may keep showing the key symbol, which is cosmetic.

Browse

All MED17 files are listed by part number and software number on the VW, Audi, Skoda and Seat pages. If your version is missing, send the original read via the file request form.

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