On Board Diagnosis Logic

NOTE: If DTC P1442 is displayed with P0447, perform trouble diagnosis for DTC P0447 first. (See DTC P0447 EVAP CANISTER VENT CONTROL VALVE .)

This diagnosis detects leaks in the EVAP purge line using vapor pressure in the fuel tank.

The EVAP canister vent control valve is closed to shut the EVAP purge line. The vacuum cut valve bypass valve will then be opened to clear the line between the fuel tank and the EVAP canister purge volume control solenoid valve. The EVAP control system pressure sensor can now monitor the pressure inside the fuel tank. If pressure increases, the ECM will check for leaks in the line between the vacuum cut valve and EVAP canister purge volume control solenoid valve.

Fig 1: EVAP Control System Diagram

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

DTC DETECTING CONDITION CHART

DTC No.	Trouble diagnosis name	DTC detecting condition	Possible cause
P1442 1442	EVAP control system small leak detected (positive pressure)	EVAP control system has a leak, EVAP control system does not operate properly.	Incorrect fuel tank vacuum relief valve Incorrect fuel filler cap used Fuel filler cap remains open or fails to close. Foreign matter caught in fuel filler cap. Leak is in line between intake manifold and EVAP canister purge volume control solenoid valve. Foreign matter caught in EVAP canister vent control valve. EVAP canister or fuel tank leaks EVAP purge line (pipe and rubber tube) leaks EVAP purge line rubber tube bent Blocked or bent rubber tube to EVAP control system pressure sensor Loose or disconnected rubber tube EVAP canister vent control valve and the circuit EVAP canister purge volume control solenoid valve and the circuit Fuel tank temperature sensor O-ring of EVAP canister vent control valve is missing or damaged Water separator EVAP canister is saturated with water EVAP control system pressure sensor Fuel level sensor and the circuit Refueling control valve ORVR system leaks

CAUTION:

Use only a genuine NISSAN fuel filler cap as a replacement. If an incorrect fuel filler cap is used, the MIL may come on.
If the fuel filler cap is not tightened properly, the MIL may come on.
Use only a genuine NISSAN rubber tube as a replacement.