UPDATE :
Could it be some kind of interference messing with the signal ?
I inserted a 0,5MΩ resistor between the Dbox output and the O2 plug to measure receiver’s impedance, and noticed something strange :
During the 10 min that I left it that way, I haven’t had a single drop ! (Sent signal was lowered to 2,2V giving a 44% ethanol content)
What’s mind bugging is that during the whole time, no drops while the connections looked like this :
(do not try to figure out color coding ^^)
Next step is to add a capacitor to smoothen the signal...
Any idea ??