Problems with the engine

Problem Possible causes/consequences and - Solutions
The engine does not start. The starter motor can be heard.  - There is a malfunction in the engine electronics.

 - There is a malfunction in the fuel supply.

•►  Before attempting to start the engine again, turn the SmartKey in the ignition back to position 0 or press the Start/Stop button repeatedly until all indicator lamps in the instrument cluster go out.

•►  Try to start the engine again (Y page 146). Avoid excessively long and frequent attempts to start the engine as these will drain the battery.

If the engine does not start after several attempts:

•►  Consult a qualified specialist workshop, e.g. an authorized Mercedes-Benz Center.
The engine does not start. You cannot hear the starter motor. The on-board voltage is too low because the battery is too weak or discharged.

•►  Jump-start the vehicle (Y page 338).

If the engine does not start despite attempts to jump-start it:

•►  Consult a qualified specialist workshop, e.g. an authorized Mercedes-Benz Center.

The starter motor was exposed to a thermal load that was too high.

•►  Allow the starter motor to cool down for approximately two minutes.

•►  Try to start the engine again.

If the engine still does not start:

•►  Consult a qualified specialist workshop, e.g. an authorized Mercedes-Benz Center.
Vehicles with a gasoline engine:

The engine is not running smoothly and is misfiring.

 There is a malfunction in the engine electronics or a mechanical component of the engine management system.

•►  Only depress the accelerator pedal slightly.

•►  Have the cause rectified immediately at a qualified specialist workshop, e.g. an authorized Mercedes-Benz Center.

Otherwise, non-combusted fuel may get into the catalytic converter and damage it.
The coolant temperature gauge shows a value above 248 °F (120 °C). The coolant level is too low. The coolant is too hot and the engine is no longer being cooled sufficiently.

•►  Stop as soon as possible and allow the engine and the coolant to cool down.

•►  Check the coolant level. Observe the warning notes as you do so and add coolant if necessary.
    See also:

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    Additives
    Only use DEF in accordance with ISO 22241. Do not use additives with DEF and do not dilute DEF with water. This may destroy the BlueTEC exhaust gas aftertreatment system. ...