A soot sensing system includes a soot sensor having a first element, and circuitry to an amount of soot accumulated on the element and to control heating of the element in response to the soot accumulation. An electrostatic repelling voltage (ERV) may be applied to a sensor/heater element(s) during a contamination prevention mode (CPM) to repel ash and reduce contamination of the sensor. A pulsed heating voltage (PHV) may be applied to the elements during the CPM and a pulsed ERV may be applied to the elements during the “off” period of the PHV. All voltage to the elements may be turned off during the CPM and the elements may be floating/ground. A PHV may be applied to the elements during the CPM and no voltage may be applied to the elements during the “off” period of the PHV. A heating voltage may be applied to the elements during a CPM corresponding to a cold start.
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