Smart Car Start / Stop Not Working

When suitable conditions are met, the Smart Car automatic start/stop system automatically switches off the engine when the vehicle stops moving and starts it up again when pulling away. Vehicle heating or climate control remain active when the engine is shut off, all other systems are shut down.


Warning Lights

You’ll see dashboard warning lights that inform you of the status of the automatic engine start / stop system.

SymbolSymbol Meaning
Smart Fortwo Start / Stop System Active Warning LightSuitable conditions have been met for the start / stop system to operate. The engine is switched off.
Smart Fortwo Start / Stop System Inactive Warning LightSuitable conditions have not been met, the engine stop inhibitor is active. The engine will not stop automatically.

Engine Start / Stop Not Working

In order for the Smart Car engine start stop system to work correctly, certain conditions must be met. Start / stop may not be working due to these conditions not being met, the driver has activated or altered a system or there’s a fault. The following conditions may provide you with some answers as to why your Smart Car start / stop is not working.

Engine Stops

If your start / stop system is not working, check the following conditions apply. When these start / stop conditions are met, the Smart Car engine stops automatically in the following situations:


  • The automatic start/stop system has been switched on.
  • The outside temperature is within the range that the start / stop system can operate. If you are driving in a very hot or very cold climate, the system may not function.
  • Atmospheric pressure is within the range that is suitable for the system. Driving at high altitude may prevent the system from operating.
  • The engine is at normal operating temperature. If the engine is running hot and requires cooling, or it is cold and has not yet reached optimal running temperatures, the start / stop system may not work.
  • The temperature in the vehicle interior has reached the set value. Engine start / stop will not switch off the engine if the interior temperature set by vehicle occupants has not been reached.
  • The battery is charged. Starting the engine uses a considerable amount of battery energy. If the battery is not in a high state of charge, start / stop will not operate.
  • The windscreen is not misted up (when the climate control system is switched on). As a safety precaution, the engine will not shut down during start / stop if the windows are misted up.
  • The doors and tailgate are closed. Ensure all doors and tailgate / boot are properly shut in order for start / stop to function.
  • The driver’s seat belt is fastened.
  • Reverse gear is not engaged.

Engine Starts

During the stop phase of start / stop, the Smart engine starts automatically in the following situations:

  • The automatic start/stop system has been switched off.
  • The clutch pedal has been depressed.
  • The brake has been depressed.
  • The vehicle is rolling.
  • The temperature in the vehicle interior differs from the set temperature. The engine may start if climate control or heating has been switched on or altered.
  • The tailgate / boot has been opened.
  • The windscreen has become misted up.
  • The battery charge is too low.