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.
Car Problem Reports
Mercedes-Benz SL550 Camshaft Adjuster Solenoid Failure
Mercedes-Benz SL550 Problem
May 13,2013 purchases 2007 Mercedes Benz SL550 hard top convertible. Drove it once that weekend. Parked it in garage. Two weeks later, took it out for a drive and check engine light came on. Took it back to Carmax, they say its a solenoid and repair is covered under warranty I purchased. My deductible is $200. Thoughts anyone ? I could not tell any difference driving because I only drove car some 50 miles total since purchasing it. Prior it was a "fleet car" with a clean car fax history.