Mercedes-Benz E-Class Coupe 2021 Operator's Manual page 402

400 Display messages and warning/indicator lamps
Warning/indicator lamp Possible causes/consequences and
If the coolant temperature display is at the lower end of the temperature scale:
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If the coolant temperature display is at the upper end of the temperature scale:
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* The yellow coolant warning lamp is lit while the engine is running.
Possible causes:
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Coolant warning lamp (yel‐
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low)
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;
* The yellow Check Engine warning lamp is lit while the engine is running.
A malfunction has occurred in the engine, the exhaust system or the fuel system.
The emission limit values may be exceeded and the engine may be in emergency mode.
Engine diagnosis warning
In some states, legal requirements stipulate that you must immediately consult a qualified specialist workshop as
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soon as the yellow Check Engine warning lamp lights up.
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Consult a qualified specialist workshop.
Exit the vehicle and keep a safe distance from it until the engine has cooled down.
Check the coolant level ( page 275).
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Make sure that the air supply to the radiator is not obstructed.
Avoiding high loads on the engine, drive to the nearest qualified specialist workshop. In doing so, ensure that the
coolant temperature display remains below the red area.
The temperature sensor is malfunctioning
The charge air, transmission oil or battery cooling is faulty
Avoiding high loads on the engine, drive to the nearest qualified specialist workshop.
Solutions