Investigating P0455 on Your 2020 Subaru Legacy
P0455 on your 2020 Legacy indicates a large EVAP system leak. This 7th-generation Legacy with the 2.5L boxer engine (or available 2.4L turbo) is out of basic warranty but emissions coverage may apply. Gas cap first.
Clues
- Check engine light with P0455
- Faint fuel smell possible
- Gas cap not clicking properly
- Emissions inspection failure
Causes Ranked
- Gas Cap Seal (Very High Likelihood): Degraded after 4+ years. $10–$25.
- Purge Control Solenoid (Medium Likelihood): Age-related sticking. $150–$280 installed.
- Vent Control Valve (Medium Likelihood): Seal deterioration. $120–$250 installed.
- Vapor Hose (Low Likelihood): Heat damage near boxer exhaust. $80–$200.
- Charcoal Canister (Low Likelihood): Saturated from overfilling. $200–$400 installed.
Diagnosis
New gas cap is the cheapest fix to try first. If P0455 returns, smoke testing is the gold standard. Subaru dealers use SSM4 for integrated EVAP diagnostics.
Warranty
Basic warranty (3yr/36k) has expired. Federal emissions warranty (8yr/80k) covers EVAP through 2028. Check your mileage with your dealer.
Safe to Drive?
Yes. P0455 doesn't affect the 2.5L boxer (or 2.4T), CVT, Symmetrical AWD, or EyeSight.