after a few runs, the oxygen sensor failed one after the other, they were both replaced for a Bosch reference 13231 (made in USA)
Now both oxygen sensors are responding accordingly so are the additive and mutliplicativ factor.
Also the B + battery short listed in the error message is not listed after a few runs with more than 10 crank and start.
I posted the pict on the bimmerforum for anyone interested
https://www.bimmerforums.com/forum/s...sensor-dilemma