On Board Diagnosis Logic

The heated oxygen sensor 2 has a much longer switching time between rich and lean than the A/F sensor 1. 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 voltage is unusually high during the various driving condition such as fuel-cut.

Fig 1: On Board Diagnosis Logic Chart

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

Fig 2: Voltage Graph For HO2S2

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