DTC P0448 Evaporative Emission Control System Vent Control Circuit Shorted

WARNING: This page is about a different car, the 2006 Subaru Outback. However, it is still accessible from the selected car via links, so may be relevant.

DTC DETECTING CONDITION:

Immediately at fault recognition
GENERAL DESCRIPTION < Ref. to DTC P0448 EVAPORATIVE EMISSION CONTROL SYSTEM VENT CONTROL CIRCUIT SHORTED , Diagnostic Trouble Code (DTC) Detecting Criteria. >

CAUTION: After repair or replacement of faulty parts, perform Clear Memory Mode < Ref. to OPERATION , Clear Memory Mode. > and Inspection Mode < Ref. to PROCEDURE , Inspection Mode. >.

WIRING DIAGRAM:

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

DTC P0448 EVAPORATIVE EMISSION CONTROL SYSTEM VENT CONTROL CIRCUIT SHORTED - DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK INPUT SIGNAL OF ECM. Turn the ignition switch to OFF. Connect the test mode connector at the lower portion of instrument panel (on the driver's side). Turn the ignition switch to ON. Measure the voltage between ECM and chassis ground while operating the drain valve. NOTE: Drain valve operation can be executed using Subaru Select Monitor. Regarding the procedures, refer to "Compulsory Valve Operation Check Mode". < Ref. to COMPULSORY VALVE OPERATION CHECK MODE . > Connector & terminal (B136) No. 17 (+) - Chassis ground (-):	Is the voltage 0 - 10 V?	Go to step 2.	Even if the malfunction indicator light illuminates, the circuit has returned to a normal condition at this time. In this case, repair the poor contact in ECM connector.
2 CHECK INPUT SIGNAL OF ECM. Turn the ignition switch to ON. Measure the voltage between ECM and chassis ground. Connector & terminal (B136) No. 17(+) - Chassis ground (-):	Is the voltage more than 10 V?	Go to step 4.	Go to step 3.
3 CHECK POOR CONTACT. Check the poor contact of ECM connector.	Is there poor contact in ECM connector?	Repair the poor contact of ECM connector.	Replace the ECM. < Ref. to ENGINE CONTROL MODULE (ECM) . >
4 CHECK HARNESS BETWEEN DRAIN VALVE AND ECM CONNECTOR. Turn the ignition switch to OFF. Disconnect the connector from the drain valve. Turn the ignition switch to ON. Measure the voltage between ECM and chassis ground. Connector & terminal (B136) No. 17 (+) - Chassis ground (-):	Is the voltage more than 10 V?	Repair the battery short circuit in harness between ECM and drain valve connector. After repair, replace the ECM. < Ref. to ENGINE CONTROL MODULE (ECM) . >	Go to step 5.
5 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 . > and ECM < Ref. to ENGINE CONTROL MODULE (ECM) . >.	Go to step 6.
6 CHECK POOR CONTACT. Check the poor contact of ECM connector.	Is there poor contact in ECM connector?	Repair the poor contact of ECM connector.	Replace the ECM. < Ref. to ENGINE CONTROL MODULE (ECM) . >