Engine

Mercedes-Benz M-Class / Mercedes-Benz M-Class Owners Manual / On-board computer and displays / Warning and indicator lamps in the instrument cluster / Engine

Display messages	Possible causes/consequences and Solutions
The yellow Check Engine warning lamp lights up while the engine is running.	There may be a malfunction, for example: - in the engine management - in the fuel injection system - in the exhaust system - in the ignition system (for vehicles with a gasoline engine) - in the fuel system The emission limit values may be exceeded and the engine may be running in emergency mode. – Have the vehicle checked as soon as possible at a qualified specialist workshop. In some states, you are required by law to immediately visit a qualified specialist workshop as soon as the yellow Check Engine warning lamp lights up. If in doubt, check whether such legal regulations apply in the state/province in which you are currently driving.
	Vehicles with a diesel engine: the fuel tank has been run dry. – Start the engine three to four times after refueling. If the yellow Check Engine warning lamp goes out, emergency running mode is canceled. The vehicle need not be checked.
The yellow reserve fuel warning lamp flashes while the vehicle is in motion. In addition, the yellow Check Engine warning lamp may light up.	The fuel system pressure is too low. The fuel filler cap is not closed correctly or the fuel system is leaking. – Observe the additional display messages in the multifunction display. – Check that the fuel filler cap is correctly closed. – If the fuel filler cap is not correctly closed: close the fuel filler cap. – If the fuel filler cap is closed: visit a qualified specialist workshop.
The yellow reserve fuel warning lamp lights up while the engine is running.	The fuel level has dropped into the reserve range. – Refuel at the nearest gas station.
The red coolant warning lamp lights up while the engine is running and the coolant temperature gauge is at the start of the scale.	The temperature sensor for the coolant temperature gauge is defective. The coolant temperature is no longer being monitored. There is a risk of engine damage if the coolant temperature is too high. – Pull over and stop the vehicle safely and switch off the engine, paying attention to road and traffic conditions. Do not continue driving under any circumstances. – Apply the electric parking brake. – Consult a qualified specialist workshop.
The red coolant warning lamp comes on while the engine is running.	The coolant level is too low. If the coolant level is correct, the airflow to the engine radiator may be blocked or the electric engine radiator fan may be malfunctioning. The coolant is too hot and the engine is no longer being cooled sufficiently. – Observe the additional display messages in the multifunction display. – Pull over and stop the vehicle safely and switch off the engine, paying attention to road and traffic conditions. – Allow the engine and coolant to cool. – Check the coolant level and add coolant. Observe the warning notes. – If you need to add coolant more often than usual, have the engine coolant system checked. – Make sure that the air supply to the engine radiator is not blocked, e.g. by snow, slush or ice. – At coolant temperatures under 248 °F (120 °C ), drive to the next qualified specialist workshop. – Avoid subjecting the engine to heavy loads, e.g. driving in mountainous terrain, and stop-and-go traffic.
The red coolant warning lamp comes on while the engine is running. A warning tone also sounds.	The coolant temperature has exceeded 248 °F (120 °C ). The airflow to the engine radiator may be blocked or the coolant level may be too low. The engine is not being cooled sufficiently and may be damaged. – Observe the additional display messages in the multifunction display. – Pull over and stop the vehicle safely and switch off the engine, paying attention to road and traffic conditions. – Allow the engine and coolant to cool. – Check the coolant level and add coolant. Observe the warning notes. – If you need to add coolant more often than usual, have the engine coolant system checked. – Make sure that the air supply to the engine radiator is not blocked, e.g. by snow, slush or ice. – At coolant temperatures under 248 °F (120 °C ), drive to the next qualified specialist workshop. – Avoid subjecting the engine to heavy loads, e.g. driving in mountainous terrain, and stop-and-go traffic.

WARNING
Driving when your engine is overheated can cause some fluids which may have leaked into the engine compartment to catch fire. You could be seriously burned.
Steam from an overheated engine can cause serious burns which can occur just by opening the engine hood. Stay away from the engine if you see or hear steam coming from it.
Stop the vehicle in a safe location away from other traffic. Turn off the engine, get out of the vehicle and do not stand near the vehicle until the engine has cooled down.

If the coolant temperature exceeds 248 °F(120 °C) do not continue driving. The engine will otherwise be damaged.

Engine

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