Patent ID: 6860144

Claim:
A non-intrusive method for detecting aging of an oxygen sensor mounted in an engine exhaust stream of a vehicle and in communication with an engine controller, the method comprising the steps of: initiating the method at the engine controller only when engine operating conditions satisfy a predetermined set of criteria whereunder the method will not intrude upon the engine controller's ability to minimize undesirable exhaust emissions; obtaining from the oxygen sensor a series of consecutive sensor output signals taken over a plurality of time blocks; summing the series of output signals for each block; determining a maximum and a minimum value of the series of output signals for each block; determining an absolute value of the difference between each pair of consecutive output signals (delta signals) in the series for each block; obtaining an average flow rate within each block; storing, for each block, the sum of the series of output signals, a sum of the delta signals, the maximum output signal and the minimum output signal; compensating the sum of the delta signals for each block in accordance with the average exhaust flow rate of the block; determining, from all blocks, an average value of the sensor output signals, an average value of compensated delta signals, an average maximum value and an average minimum value; comparing each average value determined in the preceding step to an associated test standard; and determining acceptable aging of the sensor whenever each average value compares favorably with its associated test standard.