Hello,
I have to build device based on Arduino and canbus module to monitor and react to some specyfic engine values like boost. Boost pressure value is default not sended by ecu via canbus, i must estabilish diagnosis session and ask ecu for actual boost pressure value (VW Transport Protocol). It is cleary simple, i helping myself by this tutorial: https://jazdw.net/tp20 but I stuck on first step  :cry:. If I send initialization packet (dest: 0x200   data: 01 C0 00 10 00 03 01), ecu receive them and reply with error packet (00 D8 00 what means "negative reply"). See attached video where I demonstrate this strange behavior. I tried combining with initialization packet values but with no success, ecu always reply with "negative reply" packet. Can somebody help me ?

https://www.youtube.com/watch?v=jUn43R7-vVg

Yup, I read Your thread, but in my situation ecu don't initialize diagnosis channel. Only reply that i receive from ecu is "negative reply" and next steps have no effect. Maybe failure reason is I have ecu connected only to power supply and diagnostic interface "on the desk", not in the car.