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. The oxygen storage capacity of 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: Graphing Heated Oxygen Sensor 2 (DTC P0138 & P0158)

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

Fig 2: Identifying DTC P0138 & P0158 Conditions & Possible Causes

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