On Board Diagnosis Logic

To judge the malfunction, the A/F signal computed by ECM from the air fuel ratio (A/F) sensor 1 signal is monitored not to be shifted to the lean side or rich side. When the A/F sensor 1 signal is shifting to the rich side, the malfunction will be detected.

Fig 1: On Board Diagnosis Logic

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