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DTC P0456: EVAP System Malfunction

NOTE: This diagnostic procedure is written for scan tool operation. Drain valve, purge control solenoid valve and pressure control solenoid valve can be operated by performing compulsory valve operation if Subaru Select Monitor is being used. See COMPULSORY VALVE OPERATION CHECK MODE  under SELF-DIAGNOSTIC SYSTEM.
  1. Perform test procedure. See TESTING PROCEDURE . If DTC P0456 is only DTC set, go to next step. If any other DTCs exist, diagnose and repair those DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
  2. Turn ignition off. Check fuel filler cap. If fuel filler cap is/was loose or if cap chain was caught while tightening, DTC will set. If fuel filler cap is tight, go to next step. If fuel filler cap was not tight, tighten fuel filler cap. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
  3. Check fuel filler pipe packing. If there is no damage to seal between fuel filler cap and fuel filler pipe, go to next step. If there is damage to seal between fuel filler cap, repair or replace fuel filler cap and fuel filler pipe. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
  4. Turn ignition off. Connect 2-pin Green test connector located under left side of instrument panel (near center of instrument panel on Legacy and Outback). See Figure, Figure and Figure . Turn ignition on. Using a scan tool, activate drain valve. If drain valve operates, go to next step. If drain valve does not operate, replace drain valve. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
  5. Using a scan tool, activate purge control solenoid valve. If purge control solenoid valve operates, go to next step. If purge control solenoid valve does not operate, replace purge control solenoid valve. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
  6. Using a scan tool, activate pressure control solenoid valve. If pressure control solenoid valve operates, go to next step. If pressure control solenoid valve does not operate, replace pressure control solenoid valve. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
  7. Turn ignition off. Disconnect 2-pin Green test connector. Check for any holes larger than 0.02" (0.50 mm) in fuel lines. If no holes are present, go to next step. If holes are located, repair or replace defective fuel line. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
  8. Check charcoal canister for damage or holes larger than 0.02" (0.50 mm). If canister is okay, go to next step. If canister is not okay, repair or replace charcoal canister. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
  9. Remove fuel tank. Check fuel tank for damage or holes larger than 0.02" (0.50 mm). If fuel tank is okay, go to next step. If fuel tank is not okay, repair or replace fuel tank. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
  10. Check EVAP system for holes larger than 0.02" (0.50 mm), clogging or disconnected hoses/pipes. If damage is found, repair or replace EVAP components as required. If no damage is found, contact authorized Subaru dealership because probable cause is deterioration of multiple parts. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
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