Pursuing the P0446 on Your 2020 Subaru Legacy
A P0446 code on your 2020 Subaru Legacy reveals an EVAP vent control circuit malfunction. As the first year of the seventh-generation Legacy (BN platform), your sedan's 2.5L FA25 boxer engine — or available 2.4L FA24 turbo — uses a canister vent control valve for evaporative emissions management. After five years, the ECM has detected an electrical fault in this circuit.
The BN Legacy debuted on the Subaru Global Platform, bringing improved refinement and technology. The EVAP system follows Subaru's established boxer-engine architecture.
Symptoms Observed
- Check engine light on with P0446
- Fuel nozzle clicking off prematurely
- EVAP readiness monitor not setting
- Possible faint fuel vapor smell
- May appear with P0441 or P0456
Ranked Suspects
- Canister Vent Control Valve Failure (High Likelihood): Five years of thermal cycling wears the vent valve solenoid. The most common P0446 cause on Subaru. Parts $45–$95, labor $80–$185.
- Wiring and Connector Deterioration (High Likelihood): Road salt and moisture corrode the vent valve electrical connections. Repair costs $75–$255.
- Purge Control Solenoid Issue (Medium Likelihood): The boxer engine's purge solenoid faces unique heat patterns. Replacement costs $70–$190.
- Charcoal Canister Degradation (Medium Likelihood): Five years of use and potential overfilling degrade the canister. Replacement costs $145–$315.
- Gas Cap Seal Wear (Low Likelihood): Quick check. New cap $15–$30.
Diagnostic Steps
- Try a new gas cap first
- Scan for codes and freeze frame data
- Inspect the vent valve connector at the rear
- Test vent valve resistance
- Apply 12V to verify mechanical operation
- Check wiring from the valve to the ECM
Cost Breakdown
- Vent control valve: $125–$280
- Wiring/connector repair: $75–$255
- Purge solenoid: $70–$190
- Charcoal canister: $145–$315
- Diagnostic fee: $75–$130
Can I Drive With P0446?
Yes. P0446 doesn't affect your Legacy's boxer engine, CVT, or Symmetrical AWD. Emissions-only code.
Warranty and DIY
Your 2020 Legacy is past the basic warranty but within the 8-year/80,000-mile federal emissions warranty. Check your mileage. For DIY, the vent valve is moderately accessible with basic tools.