High Speed ISO9141 Interface


This project is a high speed ISO9141 interface based on not opto-isolators but a dedicated ISO driver IC, the Motorola MC33290D.








Using a dedicated IC gives many advantages:

  • High speed operation, upto 115.2kpbs as required by VAG-COM 404
  • Electronics protection against bus short circuit.
  • Wide operating voltage

Pin 6 and 5 can inteface directly to a microprocessor but to connect to a PC’s serial port a voltage level converter as such a MAX232 must be used.

Full schematic. The schematic is release under GPL license. Anyone can use it for non commercial purpose. As this is a free project I do not provide support on this. Please read the FAQ below.

Parts List


Q: Where is the L-Line?
A: Older ECU uses the L-line to “wake-up” but now days modern ECU uses the K-line for this.

Q: Does it work with VAG-COM Release 409.1?
A: Yes.

Q: Does it work with VAG-COM Release 512.1?
A: No, this version requires an interface with build in dongle. The Key series will work with 512.1

Q: Does it have dual K-Line?
A: On 2002+ Audi A4, A6 some modules are on the second K-line (formerly L-Line). If you want to connect to the L-Line add a single pole change over switch.


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