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 1 causes the longer switching time. To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the switching response of the sensor's voltage is faster than specified during the various driving condition such as fuel-cut.

Fig 1: Graphing Heated Oxygen Sensor 2 (DTC P0139 & P0159)

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

Fig 2: Identifying DTC P0139 & P0159 Conditions & Possible Causes

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