This bulletin applies to troubleshooting DTC P0457 on 2008 and later Subaru models. When troubleshooting any evaporative system trouble code, particularly P0457, don’t forget to check evaporative system hose connections for being in their correct locations.
On occasion, technicians may find hoses switched at the canister.
For example, the vehicle may have been involved in a collision, with the hose connections accidentally switched during the repair.
With the hoses connected backwards, the drain hose goes to the fuel tank and the canister hose goes to atmospheric pressure, which eventually sets the code.