The Vanos solenoids on the S85 engine are a very common source of fault codes as the car ages. The solenoids gradually become contaminated with foreign debris circulating through the oil and will slowly degrade, eventually causing some power loss. You can test your solenoids using ISTA+ or INPA to see the quality, response time and performance of each solenoid.
Solenoid issues are likely caused by the common rod bearing and Vanos oil pump failures that these engines are known for. As the rod bearings and oil pump bearings wear, the metallic particles circulate through the solenoids and become lodged in valves, eventually causing fault codes. It's very important to address the fault codes as quickly as possible, as it could be an indication of failing rod bearings and/or a failing Vanos oil pump bearing.
