Wiring Diagram:

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Fig 1: Wiring Diagram - DTC P0457 Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)

G03830023

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE (DTC P0457)

Step		Check	Yes	No
1 CHECK FOR ANY OTHER DTC ON DISPLAY.		Is any other DTC displayed?	Inspect the relevant DTC using "List of Diagnostic Trouble Code (DTC)". < Ref. to , LIST OF DIAGNOSTIC TROUBLE CODE (DTC) . >	Go to step 2.
2 CHECK FUEL FILLER CAP. Turn the ignition switch to OFF. Check the fuel filler cap. NOTE: The DTC is stored in memory if fuel filler cap is or was loose or if the cap chain was caught while tightening.		Is the fuel filler cap tightened securely?	Go to step 3.	Tighten fuel filler cap securely.
3 CHECK FUEL FILLER CAP.		Is the fuel filler cap SUBARU genuine?	Go to step 4.	Replace with a SUBARU genuine fuel filler cap.
4 CHECK FUEL FILLER PIPE PACKING.		Is there any damage to the seal between fuel filler cap and fuel filler pipe?	Repair or replace the fuel filler cap and fuel filler pipe. < Ref. to FUEL FILLER PIPE . >	Go to step 5.
5 CHECK DRAIN VALVE. Connect the test mode connector. Turn the ignition switch to ON. Operate the drain valve. NOTE: Drain valve operation can also be executed using Subaru Select Monitor. For the procedure, refer to COMPULSORY VALVE OPERATION CHECK MODE .		Does the drain valve operate?	Go to step 6.	Replace the drain valve. < Ref. to DRAIN VALVE . >
6 CHECK PURGE CONTROL SOLENOID VALVE. Operate the purge control solenoid valve. NOTE: Purge control solenoid valve operation can also be executed using Subaru Select Monitor. For the procedure, refer to , LIST OF DIAGNOSTIC TROUBLE CODE (DTC) . >		Does the purge control solenoid valve operate?	Go to step 7.	Replace the purge control solenoid valve. < Ref. to PURGE CONTROL SOLENOID VALVE . >
7 CHECK PRESSURE CONTROL SOLENOID VALVE. Operate the pressure control solenoid valve. NOTE: Pressure control solenoid valve operation can also be executed using Subaru Select Monitor. For the procedure, refer to COMPULSORY VALVE OPERATION CHECK MODE .		Does the pressure control solenoid valve operate?	Go to step 8.	Replace the pressure control solenoid valve. < Ref. to PRESSURE CONTROL SOLENOID VALVE . >
8 CHECK CANISTER.		Is the canister damaged?	Repair or replace the canister. < Ref. to CANISTER . >	Go to step 9.
9 CHECK FUEL TANK. Remove the fuel tank. < Ref. to FUEL TANK . >		Is the fuel tank damaged?	Repair or replace the fuel tank. < Ref. to FUEL TANK . >	Go to step 10.
10 CHECK ANY OTHER MECHANICAL TROUBLE IN EVAPORATIVE EMISSION CONTROL SYSTEM.		Are there holes of more than 0.5 mm (0.020 in) dia., cracks, clogging, or disconnections, misconnection of hoses or pipes in evaporative emission control system?	Repair or replace the hoses or pipes.	Contact with SOA Service Center.