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 "lean" side or "rich" side. When the A/F signal is shifting to the lean side, the malfunction will be detected.

Fig 1: DTC Trouble Detection Chart

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