On Board Diagnosis Logic

To judge the malfunction, the output from the heated oxygen sensor 1 is monitored to determine whether the rich output is sufficiently high and whether the lean output is sufficiently low. When both the outputs are shifting to the lean side, the malfunction will be detected.

Fig 1: Heated Oxygen Sensor Output Voltage Graph

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

Fig 2: On Board Diagnosis Logic

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