On Board Diagnosis Logic

This diagnosis detects very small leaks in the EVAP line between the fuel tank and the EVAP canister purge volume control solenoid valve using intake manifold vacuum in the same way as conventional EVAP small leak diagnosis.

If the ECM judges a leak equivalent to a very small leak, the very small leak DTC P0456 or P1456 will be detected. If the ECM judges a leak equivalent to a small leak, the EVAP small leak DTC P0442 will be detected. Correspondingly, if the ECM judges there is no leak, the diagnosis result is OK.

Fig 1: EVAP Control System Diagram

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

Fig 2: DTC Detecting Condition Chart

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