On Board Diagnosis Logic

The heated oxygen sensor 2 has a much longer switching time between rich and lean than the air fuel ratio (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 maximum voltage of the sensor is sufficiently high during the various driving condition such as fuel-cut.

Fig 1: Diagnostic Chart

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

Fig 2: Identifying Voltage Cycle

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