DTC P0448 Evaporative Emission Control System Vent Control Circuit Shorted: Wiring Diagram

Fig 1: Evaporative Emission Control System Vent Control - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK HARNESS BETWEEN ECM AND DRAIN VALVE.  Turn the ignition switch to OFF. Disconnect the connectors from the ECM and drain valve. Turn the ignition switch to ON. Measure the voltage between ECM and chassis ground. Connector & terminal  (B135) No. 4 (+) - Chassis ground (-):	Is the voltage 10 V or more?	Repair the short circuit to power in the harness between ECM and drain valve connector.	Go to step 2.
2 CHECK DRAIN VALVE.  Turn the ignition switch to OFF. Measure the resistance between drain valve terminals. Terminals  No. 1 - No. 2:	Is the resistance less than 1 Ω?	Replace the drain valve. Ref. to DRAIN VALVE .	Repair the poor contact of ECM connector.