Mercedes-Benz E-Class Operator's Manual page 409

Engine
Warning/indicator lamp
;
Engine diagnosis warning
lamp
Possible causes/consequences and
The yellow engine diagnosis warning lamp is lit while the engine is running.
A malfunction has occurred in the engine, the exhaust system or the fuel system.
The emissions limit values may be exceeded and the engine may be running in emergency operation mode.
In some states, legal requirements stipulate that you must immediately consult a qualified specialist workshop as soon
as the yellow engine diagnosis warning lamp lights up.
Have the vehicle checked as soon as possible at a qualified specialist workshop.
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Display messages and warning/indicator lamps 407
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