Since existing info on these cars fiber optic stereos basically sucked, here's a new video series showing you 1) how they work, and how to diagnose and fix a common problem with a 2003 - 2005 factory BOSE W220 S500, S430, S600, and S55 BOSE Comand radio and NAV head unit that indicates a "System Unavailable" message on screen, then powers down and shuts off. The most probable issue is likely a damaged Becker AGW BE 7003 BASIS audio gateway (AGW) unit! The gateway is the Comand head unit's remotely located "pre-amp" unit which processes all car audio, phone audio, crossover, Teleaid, etc, and can easily be replaced for about $200 USD on Ebay. SYMPTOM: If the head unit powers on and then shuts off, its very likely NOT the COMAND head unit itself which has failed. First, please check all the fuses as shown in my part 2 video. It's NOT the car battery causing problems if your car will start! This MOST ring theory also applies to most E series like E300, E430, E55 AMG, E500 and many other Audi, BMW, VW, and Benz models. 2) Fix the Audio Gateway (AGW), location and tips for fuses, and all about the fiber optic MOST ring is also covered. 3) Bonus: massively over complex and long explanation of the entire system, with part 2 also discussing replacing the entire radio with aftermarket setup from China. Make your BENZ great again and watch this deplorable video!