Filler cap sensor


Due to the North American regulation regarding evaporative emission control generated in the area of the fuel tank, for example, a German car manufacturer required gas cap lock detection for the SCR fuel system.


The requirements for the gas cap detection included:

  • capability for on-board diagnosis
  • opening of the gas cap is also detected when the ignition is turned off
  • extremely low power consumption to conserve battery life
  • resistant to environmental influences (e.g. contact with gasoline/diesel or water/salt)


The requirements were met with active electronics enclosed in an injection molding.

The electronics will go into sleep mode when the ignition is turned off. The quiescent current consumed in sleep mode is extremely low at ~30µA. If the gas cap is opened, the electronics will store this incident and transmit it to the engine control unit once the ignition is turned back on.

An injection molding was designed for the housing into which the electronics are embedded. This way it is ideally protected against contact with gasoline, water and even dust.