Crossover Count

The O2 sensor voltage fluctuates around a threshold voltage: the value of which is stored in the PROM. A counter within the ECM `counts' the number of times that actual oxygen sensor voltage crosses this threshold to indicate how fast the sensor is oscillating. The crossover count is the a value representing the number of times that the sensor value crosses this threshold in 1.25 seconds. A higher crossover count number indicates a more closely air/fuel mixture ratio.