Method for operating a heating element in a motor vehicle by means of pulse width modulation

The PWM based operating method involves measuring a voltage present at a heating element (R) e.g. glow plug and/or a current flowing through the heating element at specified intervals during a voltage pulse application. Measured values or corresponding values determined from the measured values are added to calculate a sum value. The sum value increases with energy fed into the heating element through the voltage pulse application. The voltage pulse application is ended when the sum value has reached a target value.