On Board Diagnostic (OBD) System: Introduction

The ECM has an on board diagnostic system, which detects malfunctions related to engine sensors or actuators. The ECM also records various emission-related diagnostic information including:

Fig 1: On Board Diagnostic System -Emission Related Diagnostic Problem

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

The above information can be checked using procedures listed in the table below.

Fig 2: Checking Procedure Table

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

The malfunction indicator lamp (MIL) on the instrument panel lights up when the same malfunction is detected in two consecutive trips (Two trip detection logic), or when the ECM enters fail-safe mode. (Refer to Description .)