Reading is easy via OBD but it took almost a Hour to do, where writing takes 3 min approx. BUT you need to put the ECU into Programming mode manually, in the Kess manual says: Short Pin 3 of the first plug on the ECU to +12 and pin1 with pin16 on the diag.plug.. So you have litteraly a swich wich when you put power on it gets into programing mode and you will be able to write it.
After 2m of wire and 10min of my time i figured it out how to write this Ecu, so it is possible without opening or taking it of the Car
Tip: when you want to write by Kess v2 ECU programmer just make the writing setting of kess v2 to minimum speed and resistor setting to 380 ohms or so , and follow the instructions , at a time you will be asked to put ignition on and close the programming switch (which is putting jumper wire ) between 3,5 pin at the the first left connector (red and yellow at my E55) you can see the fan kiked in and complete instructions ,