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Bosch MED17.5, MED17.5.1, 5.2, 5.5, 5.20, 5.21, 5.25 (Audi, Seat, Skoda, Volkswagen): BSL connections

Connection diagrams for the Volkswagen group MED17.5 units, the most common petrol family on Golf, Polo, Ibiza, Fabia and mid-capacity Audis. Nearly every entry also has a BSL connection for boot mode.

Procedure

1. Pin down the exact designation from the label: MED17.5 TC1766 (Volkswagen, Seat, Skoda, Audi), MED17.5.1 TC1796 and TC1766 (Volkswagen), MED17.5.2 TC1767 (Audi, Seat, Skoda, Volkswagen), MED17.5.5 TC1766 and TC1767 (Audi, Seat, Skoda, Volkswagen), MED17.5.20 TC1766 (Audi, Seat, Volkswagen), MED17.5.21 TC1782 (Audi, Seat, Volkswagen, Skoda), MED17.5.25 TC1782 (Audi, Skoda, Seat, Volkswagen).
2. Open the ECU and read the Tricore microcontroller part number so you pick the right variant when the manual lists more than one.
3. Go to the entry's page and locate the base diagram and the "BSL connection" section, present on MED17.5.1, MED17.5.2, MED17.5.5, MED17.5.20 and MED17.5.25.
4. Wire the points shown in the drawing respecting pins and wire colours; where the drawing shows points on the board, make the solder joints carefully and avoid bridging adjacent pads.
5. Add the BSL connection if you need to work in boot mode, then re-check the whole loom with the ECU unpowered.
6. Power the ECU on the bench, connect the AVDI and start the read from the software.
7. Save the original file you read out and keep it before moving on to the write.

Reference screenshots