Hi guys how this sounds crazy but....my radiator cap was bad it sucked my hoses vacuum....
Besides i solved my P0420 code its just for the info i ve monitored the second 02 sensor and it stays stable....so maybe this info helps for you guys outthere

 

I don’t understand. How did it suck your vacuum hose?

 

Well the valve in the cap did not function i looked it up on the net and found out during cooling down it can happen

 

i think he means the cap was causing a vacuum to occur on cooldown and collapsing his coolant hoses. Dont know how that affects the obd2 system other than delayed warmup or overheat causing the temps to change rapidly and the ecm fueling that the O2 sensors read

 

This is what i ment with the cap and for the OBD system.....
Well me neither but since then i have no MIL that's why I came to this conclusion... I drove the car for then till now 300 kilometres in miles I think around 150ish???

 

Ah I see. Glad to hear that you’ve fixed the problem.