P0456 on Your 2020 Legacy: Following the Evidence
Your 2020 Legacy (8th generation—first year of the redesign) has triggered P0456—a very small EVAP leak. The 2.5L Boxer (or 2.4L turbo XT) with Symmetrical AWD uses a traditional gas cap and standard EVAP system. Basic warranty expired, but federal emissions (8yr/80k) covers EVAP through 2028.
Clues
- Check engine light on
- P0456 stored
- No performance symptoms
- Gas cap may show wear after 5+ years
Suspects
- Gas Cap Seal (High Likelihood): Five years of wear. $10–$15.
- Purge Control Solenoid Valve (High Likelihood): Known Subaru failure—TSBs exist for this platform. Under emissions warranty or $90–$210.
- Canister Vent Valve (Medium Likelihood): Age-related. Under emissions warranty or $100–$230.
- EVAP Hose (Medium Likelihood): Rubber deterioration. $110–$240.
- Charcoal Canister (Low Likelihood): Fuel overfilling saturation. $200–$380.
Diagnostic Steps
- Replace gas cap—$10–$15
- Clear code, drive 2–3 cycles
- Check federal emissions warranty—8yr/80k through 2028
- Dealer appointment—ask about first-year platform TSBs
- Smoke test if out-of-pocket ($80–$150)
Costs
- Gas cap: $10–$15
- Purge valve: $90–$210 (may be emissions covered)
- Canister vent valve: $100–$230
- Federal emissions 8yr/80k through 2028
Can I Drive?
Yes. P0456 has zero impact on the Boxer engine, AWD, or EyeSight.
Warranty
Basic 3yr/36k expired. Powertrain 5yr/60k expired. Federal emissions 8yr/80k covers EVAP through 2028. First year of redesign—ask about applicable TSBs.