KKL/KL Diagnosis: Causes & Treatment

Hello everyone,
I would like to try building a working diagnostic interface again soon. My TDI (manufactured in April 1994) still has the old 2x2 connector, but I would like to build an "upgradeable" interface that also supports newer vehicles with two K-lines.

Is that possible? What would happen to the second K-line if the interface is only connected to the old system? Would it remain free?

The whole thing sounds very complicated just from the idea of it.

Tino Kossmann wrote:

Hello everyone, I would like to start a second attempt soon to build a working diagnostic interface. My TDI (manufactured in 04/1994) still has the old 2x2 connector, but I would like to build a "future-proof" interface that also supports newer vehicles with two K-lines.

Hi Tino,

Some of the adapter circuits in my diagnostic article are designed for KK.
They don't care whether they are communicating with one or two vehicle-side K-lines.

I also once redrew the "Adapter 3.1 without MAX and without optocouplers" for KK and attached it here in the forum for download in December (?). -> Use the search function .

Hi Ulf,
Now I see it... I was searching for "KKL" in the schematic collection... "KK" would probably have been more effective .

So, would you recommend the "Worst Case 4.0" as a "perfect interface" to me?