2001 Mercedes SL 500 Service Light or Flexible Service System (FSS):
Sometimes referred to as the service or oil change light.  The FSS permits a flexible service schedule that is directly related to the operating conditions of the vehicle.  

The symbol (single wrench) or (double wrench) appears in the main odometer display field prior to the next suggested service.

Depending on operating conditions throughout the year, the next service is calculated and displayed in days (clock w/ single wrench)  or distance (single wrench) remaining.

The symbols (single wrench) or (double wrench) indicate the type of service to be performed:

The message is displayed for approximately 10 seconds when turning the key in the steering lock to position 2 or while driving when reaching the service warning threshold. It can be canceled manually by pressing button (1) (refer to image).  

Once the suggested term has passed, the message plus a wrench symbol preceded by a – (minus symbol) blinks for approximately 30 seconds, and a signal sounds every time when turning the key in the steering lock to position 2.

The FSS display can also be called up for approximately 10 seconds, with the display illuminated by pressing button (1) twice within 1 second.

Service A – Oil & Filter Change (typically once a year)
Service B – Oil & Filter Change, Major Filters, Vehicle Inspection, and any other time or milage-based services (typically once every 2 years)

2001 Mercedes SL Service Light Reset Instructions

1. Switch the ignition on (do not start the engine) and immediately press the knob to the left of the speedometer twice within 4 seconds.
2. Present status for days or distance is now displayed. Within 10 seconds, turn the key in the steering wheel lock to position 0.
3. Press and hold the button to the left of the speedometer while turning the key in the steering lock to position 2 again. The present status for days or distance is displayed again. Continue to hold the button until you hear a signal (approximately 10 seconds).
4. Release button.
5. The service interval displays the reset interval.
6. Turn the ignition off and then start the engine to verify the indicator has been reset.