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 minimum voltage of sensor is sufficiently low during the various driving condition such as fuel-cut.

Fig 1: Graphing Heated Oxygen Sensor 2 Normal & Out Of Specifications Signals

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

Fig 2: Identifying DTC P1146 & 1166 Conditions & Possible Causes

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