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 (A/T models ULEV and M/T models) or the air fuel ratio (A/F) sensor 1 (A/T models except ULEV). The oxygen storage capacity before the three way catalyst (manifold) causes the longer switching time. To judge the malfunctions of rear heated oxygen sensor 2, ECM monitors whether the voltage is unusually high during the various driving condition such as fuel-cut.

Fig 1: HO2S2 Switching Time Pattern

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

Fig 2: DTC P0138: Detection Condition Chart

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