A method for operating a
broadband lambda sensor for determining the concentration of
oxygen in the
exhaust gas of an
internal combustion engine operated with a fuel-air mixture is provided. In this method, a pump
voltage (UP) is applied to the pump
cell of the sensor, this
voltage-being set dependent on a Nernst
voltage (UN) tapped at the Nernst
cell, and, dependent on the
oxygen content of the
exhaust gas, driving a cathodic or anodic pump current IP via the pump
cell. In order to maintain the measurement sensitivity of the sensor even during secondary
fuel injection in lean operation and / or in “fast light off” operation, the polarity of the pump voltage (UP) is repeatedly reversed during the duration of a secondary
fuel injection and / or of the “fast light off” operation, so that an anodic pump current briefly arises that pumps
oxygen ions into the measurement chamber, occupied by the measurement
electrode of the Nernst cell and the inner
electrode of the pump cell, in which chamber the
oxygen ions oxidize the hydrocarbons.