There are a few symptoms that can develop in the E46 M3 relating to the vanos system over the course of ownership. If you experience a rattle, or constant check engine lights relating to the vanos while operating your M3 you may be in store for some periodic maintenance.

The vanos solenoid packs tend to “fry” inside causing improper operation of the vanos solenoid pack. Other more involving repairs can involve a broken cam gear, or loosening vanos bolts. The cam gear bolts should also be checked during a valve cover replacement of valve adjustment.

E46 M3 Vanos issues