On Board Diagnostic System Function

The on board diagnostic system has the following four functions.

Fig 1: On Board Diagnostic System Function Chart

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

• When there is an open circuit on MIL circuit, the ECM cannot warn the driver by lighting MIL up when there is a malfunction on engine control system.

  Therefore, when electrically controlled throttle and part of ECM related diagnosis is continuously detected as NG for 5 trips, ECM warns the driver that engine control system has a malfunction and MIL circuit is open by means of operating fail-safe function.

  The fail-safe function also operates when above diagnoses except MIL circuit are detected and demands the driver to repair the malfunction.

  Fig 2: Engine Operating Condition Chart

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