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 of the three way catalyst 1 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.