On Board Diagnosis Logic

To judge the malfunction of A/F sensor 1, this diagnosis measures response time of the A/F signal computed by ECM from the A/F sensor 1 signal. The time is compensated by engine operating (speed and load), fuel feedback control constant, and the A/F sensor 1 temperature index. Judgment is based on whether the compensated time (the A/F signal cycling time index) is inordinately long or not.

Fig 1: DTC P1278, P1288 A/F Sensor 1 - On Board Diagnosis Logic

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