1. The illumination for the radio has a different power source. Its possible for the screen to light up even if you dont have power to the radio. There is a fuse at the back of the radio, you might want to check on that one too. Switch on the ignition, check your glove compartment light or cigar lighter, if they dont work, check Fuse #4. The radio does not have a code.

2. Oil leaks. Could be your oil cooler hose. Ive replace mine three times already. Its leaking again. Id be surprised if your MB diesel didnt leak any fluid.

3. Sunroof. Your motor gear could be giving up. I replaced mine 15 yrs ago. I had the same symptoms as yours. The only way to find out is opening up your sunroof motor and look at that gear. You'll see it right away. Its that big white plastic gear. They wear out. You can purchase just that gear. Your motor seems fine.

4. Vacuum problems. Check out the archives. There is a lot of info on that topic here.

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'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles