can someone give me some advice on this, ive got a e240 v6 which began showing po422 a number of weeks ago, a friend said it was nothing to worry about as the cats are not rattling so its probably a faulty o2 sensor. today the car seemed to go into limp mode and is running rough when accelerating hard it will just stall. it will idle but sounds like a diesel... could it be a blockage from the cat breaking down. ?