How to clear check engine light on Mercedes 2003 C320 quick and free

I had a modern motorcycle, that had like 14 sensors in it.....

1. incoming air temperature.
2. Head temperature.
3. O2 exhaust gas sensor.
3. and about 8 or 9 others I can't recall right now.

And about 400 miles of wiring.

All I wanted to do is convert it all to analogue - with points and coil ignition, and a carburettor.

I see much advantage in joining vintage car clubs.....

If you can do that with that car, there's a problem with it.
I've come across that nasty engine light several times for "Something stupid" and that hack never worked. Several ecu's.
A 15€ OBD2 from Amazon does the job. (Doesn't work on a 2000 twingo, Amazon special remember, Mercedes and BMW works fine)