P0456 on Your 2020 Ascent: Tracking the Leak
Your 2020 Ascent (1st generation—Subaru's 3-row family SUV) has triggered P0456—a very small EVAP leak. The 2.4L turbocharged Boxer with Symmetrical AWD uses a standard EVAP system. Basic warranty expired, but federal emissions (8yr/80k) covers 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): Turbo heat cycling accelerates failure. Under emissions warranty or $100–$230.
- Canister Vent Valve (Medium Likelihood): Age-related. Under emissions warranty or $110–$240.
- EVAP Hose (Medium Likelihood): Rubber deterioration, turbo heat. $120–$260.
- Charcoal Canister (Low Likelihood): Fuel overfilling on the large tank. $220–$400.
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 Ascent-specific EVAP TSBs
- Smoke test if needed ($80–$150)
Costs
- Gas cap: $10–$15
- Purge valve: $100–$230 (may be emissions covered)
- Canister vent valve: $110–$240
- Federal emissions 8yr/80k through 2028
Can I Drive?
Yes. P0456 has zero impact on the turbo Boxer, AWD, towing, or safety systems.
Warranty
Basic 3yr/36k expired. Powertrain 5yr/60k expired. Federal emissions 8yr/80k covers EVAP through 2028. The Ascent was Subaru's first turbo-only model—ask about applicable TSBs.