Mercedes-Benz GLS 2020 Operator's Manual page 561

Warning/indicator lamp Possible causes/consequences and
8
The yellow fuel reserve warning lamp lights up while driving.
*There has been pressure loss in the fuel system. The fuel filler cap is not closed correctly or the fuel system is leak‐
ing.
Fuel reserve warning lamp
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If the fuel filler cap has already been closed correctly:
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8
The yellow fuel reserve warning lamp is lit while the engine is running.
* The fuel supply has dropped into the reserve range.
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Fuel reserve warning lamp
M M
Close the fuel filler cap.
Visit a qualified specialist workshop.
Refuel.
Display messages and warning/indicator lamps 559
Solutions