Odd intake flap, egr, throttle

Hello everyone!I'm working on a 2013 Mercedes Vito 113, 639 model.It has an electric motor that drives the intake flaps... also egr and throttle are electric driven. All these 3 components are powered by the same 5v ref. Also on the same 5 volt ref is the oil dash warning light.If I unplug the flaps connector the egr and throttle acts normally (key on: it moves fully close and fully open position), and the 5v ref is maintained. With the flaps connector pluged the egr and throttle valves opens an closes, continously, very short, about 10%. It drives the 5v ref down for about 1/4 of a second, to ~2.5v, then up again and again.The fist thought was that I have a bad flaps electric motor that when the ecu is trying to command brings my 5v ref down. Replaced it = same issue.Ground is good.What am I missing. Bad power/ground on ecm?

Ps: sorry for my English, it's not my home language.