code might not clear if the problem isn't resolved and it's a perm. fault. The air mass meter could be at fault too. Make sure your throlle plate is nice and clean too. The fault ocours when the O2 sensor doesn't give the reading the contol unit is expecting based on the other sensors signals, mainly the air mass meter. We've seen a few manifold gaskets and leaking injector seals give simalar codes. Usually on the 850 it's the vacuum elbows that deteriorate, eiter by the power steering pump, under the intake manifole or throttle assembly. get yourself a big can of carb. cleaner and go to town