The camshaft adjuster solenoid (which is related to the variable valve timing system) may fail or timing chain/balance shaft components may wear, resulting in illumination of the Check Engine Light and various drivability issues. Mercedes-Benz has released a service bulletin outlining specific repair instructions depending on fault codes stored.Google+
Car Problem Reports
Mercedes-Benz S550 Camshaft Adjuster Solenoid Failure
Mercedes-Benz S550 Problem
Average Mileage: 84,654 mi (63,000 mi - 102,000 mi)
Visitor, 2007 Mercedes-Benz S550, 102,000 mi
All the same damn problems. One after another. Car cost way too much to have all these damn problems. Mercedes Benz should be ashamed of themselves. Someone or all @ Mercedes need their asses kicked or do something about it!!. MAJOR RECALLS!!
Visitor, 2012 Mercedes-Benz S550
Check Engine Light came on shortly after purchased the vehicle. The dealer said it was always a emission issue and the gas cap was probably not on tight. This was not the case. The 2nd time it went in the shop for the engine light, the dealer said an update had to be installed. The 3rd time the engine light came on, they said it was a part that had to be replaced. The 4th time, they replaced another part, and it seems to have worked this time.
Visitor, 2007 Mercedes-Benz S550, 87,625 mi
check engine light on and stayed on
Visitor, 2007 Mercedes-Benz S550, 83,300 mi
S550 4MATIC; The sensor for the idler pulley was causing a failure; dealership changed the solenoids, which didnt fix the problem, now they want to dig deeper into the engine! Pretty sure Mercedes doesn't want to recall the part because of cost and reputational damage but it is a common problem