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 of the three way catalyst causes the longer switching time. To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the minimum voltage of sensor is sufficiently low during the various driving condition such as fuel-cut.

Fig 1: Voltage Cycle Graph

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

Fig 2: Diagnostic Chart

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