Problem solved, or at least postponed.
today I invested 40$ and got my code read by a shop and the fault code was (021) 15 Hydraulic Pump Relay, Activation. Apparently this error is stored 41 times in the cpu.
I don't know what to think, as soon as they erase the code, the light went off and so far hasn't turn on yet.
Before changing the relay I did a SMG reset by pulling the two flaps and disconnected the battery. Probably then the errors stored were erased?
I then changed the relay but the light was still on. I probably should have disconnected the battery again then.