On Board Diagnosis Logic

The heated oxygen sensor 2 has a much longer switching time between rich and lean than the heated oxygen sensor 1 (A/T models ULEV and M/T models) or the air fuel ratio (A/F) sensor 1 (A/T models except ULEV). The oxygen storage capacity before the three way catalyst (manifold) causes the longer switching time. To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the switching response of the sensor's voltage is faster than specified during the various driving condition such as fuel-cut.

Fig 1: Heated Oxygen Sensor Output Voltage

Courtesy of NISSAN MOTOR CO., U.S.A.

Fig 2: On Board Diagnosis Logic

Courtesy of NISSAN MOTOR CO., U.S.A.