I had a minor fender bender and took the car to the body shop. They took out the headlights to do their work. When they reinstalled them, they had to reset the car's computer in some way to have it properly recognize the headlights. When doing that, the side marker light came on again.

When the computer detects a burnt bulb or other issue, it turns the power off to that circuit. To reinitialize that circuit, the computer needs a reset.

Take your car to your Indy with the STAR system, or take it to the dealer. Its a 15 min fix.

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1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI