The most common problems with the Mercedes-Benz S550 luxury sedan are with its transmission, according to car repair statistics site CarComplaints.com. These problems are most prevalent in the 2007 model year. Other common issues include trim falling off of doors and problems with electrical accessories.
The Mercedes-Benz S550 has had few model-wide maintenance issues overall, with transmission difficulties being both the most common and most serious problem. The S550's automatic transmission shifts very abruptly and roughly, with some owners noting this issue often occurring after the vehicle is parked on a hill or incline. The transmission may also become stuck in second gear until the car is turned off and back on, presenting a potential safety issue in traffic or when merging onto a highway. Several owners have reported that replacing the throttle body valves seems to fix the issue. Others have had to replace the transmission, a potentially expensive procedure for out-of-warranty vehicles.
Accessory problems with the S550 have been rare and relatively mild. Some owners report difficulty with the car's integrated garage opener not functioning correctly or ceasing to function altogether. These issues usually require the replacement of the rear-view mirror where the garage door opener interface is located.