Self-diagnosis of a particle sensor may be used for determining a particle content in a gaseous stream. The particle sensor may include at least two interlocking, interdigital electrodes and a heating element. The heating element may be separated from the electrodes by an insulation layer. The particle sensor may be heated in a regeneration phase and a soot load on the particle sensor can thereby be removed. A semiconductive layer may be formed in the insulation layer directly beneath the electrodes by means of external doping or auto-doping. To perform a self-diagnosis, a measurement voltage may be applied at least periodically between the electrodes and a self-diagnostic current may be measured.