E90 valvetronic problem?

[Pearwhyne]

hi guys,i got engine light on my E90. the one with half filled engine on instrument cluster. it was the second time it happens. at first, came on out of the blue. got it read by a friend of mine and deleted as it happened before oil+filter change which was overdue. this time around it happened just after i start the engine in a rainy day after running a quick errands in the city and this time the car lost its power for few minutes before it turned around. no other problem i.e erratic rpm etc. hooked up to the computer by my good friend and he told me the valvetronic problem(came up 6 times before apperently) + o2 sensor. Error cleared and took the car for a spin. seems ok. got it usual power. so is this really a valvetronic problem and if so how much am i looking at if it does need valvetronic replaced? or is there anyway to salvage it i.e give it a clean etc??many thanks