Patent ID: 8906213

Claim:
A NOx sensor control apparatus which is connected to a NOx sensor, the NOx sensor having a NOx sensor element which comprises: an oxygen concentration detection cell which has an oxygen ion conductive solid electrolyte and a pair of electrodes, and generates an output corresponding to oxygen concentration in a gas to be measured which is introduced into a first measuring chamber; a first pumping cell which has an oxygen ion conductive solid electrolyte and a pair of electrodes, adjusts oxygen concentration in the first measuring chamber by pumping out or pumping in oxygen in the gas to be measured which is introduced into the first measuring chamber such that the output of the oxygen concentration detection cell becomes a predetermined value, and allows an output corresponding to the oxygen concentration in the gas to be measured; a second pumping cell which has an oxygen ion conductive solid electrolyte and a pair of electrodes, and allows a pumping current corresponding to NOx concentration in the gas to be measured which flows into the NOx measuring chamber from the first measuring chamber and has oxygen concentration thereof adjusted to flow therein; and a heater, the first pumping cell, the oxygen concentration detection cell and the second pumping cell are sequentially arranged from a distal end side along the axial direction of the NOx sensor element, the NOx sensor control apparatus comprising: a first impedance detection means which detects first impedance of a first cell which is constituted of one of the oxygen concentration detection cell, the first pumping cell and the second pumping cell; a heater control means which performs an energization control of the heater such that the first impedance of the first cell becomes a target value; a second impedance detection means which detects second impedance of a second cell which is constituted of one of the oxygen concentration detection cell, the first pumping cell and the second pumping cell, and differs from the first cell; and an output correction means which corrects at least an output of a third cell which differs from the first cell and the second cell based on the deviation between the first impedance and the second impedance.