Q: My 1988 Mercedes repair code on dash reads 409, what is this?

In 1988 Mercedes did not display trouble codes on the dashboard. The display you are seeing is a maintenance reminder. It counts the miles down until a scheduled service, then counts the miles up when you have passed the service without resetting the system. One wrench is a minor service, two wrenches means a major service. If you are sure the battery is fully charged and your starter does not operate, the first thing to try is shifting the car from Park to Neutral. If the car then cranks, you have a problem in your neutral safety switch. Other places to look for trouble are the starter relay and the starter itself. These can be diagnosed by a technician armed with a digital voltmeter. If you want to have this diagnosed you can contact Your Mechanic to have a technician come to your home or office to check out your Mercedes and advise you as to what to do next.