Diagnosing P0455 on Your 2020 Subaru Impreza
P0455 on your 2020 Impreza means the ECM detected a large EVAP system leak. Whether you have the sedan or hatchback with the 2.0L boxer engine, the diagnosis is the same. Start with the gas cap.
Symptoms
- Check engine light with P0455
- Possible fuel odor
- Gas cap loose or worn
- Failed emissions test
Causes by Likelihood
- Gas Cap Seal (Very High Likelihood): Worn after 4+ years. $10–$25.
- Purge Control Solenoid (Medium Likelihood): Sticking on the 2.0L boxer. $140–$260 installed.
- Vent Control Valve (Medium Likelihood): Near charcoal canister. $120–$240 installed.
- Vapor Line (Low Likelihood): Cracked from age/heat. $80–$180.
- Charcoal Canister (Low Likelihood): Saturated from fuel overfilling. $200–$380 installed.
Diagnostic Approach
Replace the gas cap and drive 2–3 days. If P0455 returns, a smoke test will find the leak. Subaru dealers use SSM4 diagnostics. Independent shops with smoke machines work equally well.
Warranty
The basic warranty (3yr/36k) has expired. The federal emissions warranty (8yr/80k) covers EVAP components through 2028. Check your mileage.
Safe to Drive?
Yes. P0455 is vapor only. The 2.0L boxer, CVT, Symmetrical AWD, and all systems operate normally.