Investigating the P0446 on Your 2020 Subaru Ascent
Your 2020 Subaru Ascent has triggered a P0446 code — an EVAP vent control circuit malfunction. Subaru's largest vehicle, the Ascent is powered exclusively by the 2.4L FA24 turbocharged boxer engine paired with a Lineartronic CVT and Symmetrical AWD. The canister vent control valve manages evaporative emissions, and the ECM has found an electrical fault in this circuit after five years of service.
The Ascent's three-row SUV size means longer EVAP system routing and more wiring to potentially encounter road exposure issues. Let's trace the evidence.
Symptoms You've Seen
- Check engine light on with P0446
- Fuel nozzle clicking off during fill-ups
- EVAP readiness monitor not completing
- Possible faint fuel vapor smell from the rear
- May appear with P0441 or P0455
Ranked Causes
- Canister Vent Control Valve Failure (High Likelihood): Five years of thermal cycling and road exposure wear the vent valve solenoid. The Ascent's turbo engine generates more heat, stressing nearby components. Parts $50–$100, labor $90–$200.
- Wiring and Connector Corrosion (High Likelihood): The Ascent's longer wheelbase means extended wiring runs. Road salt and moisture corrode connections over time. Repair costs $85–$275.
- Purge Control Solenoid Issue (Medium Likelihood): The FA24 turbo's purge solenoid faces higher temperatures than naturally aspirated Subaru engines. Replacement costs $80–$210.
- Charcoal Canister Degradation (Medium Likelihood): The turbo engine generates more fuel vapors, putting extra demand on the canister. Canister replacement costs $155–$340.
- Gas Cap Seal Wear (Low Likelihood): Quick, inexpensive check. New cap $15–$35.
Diagnostic Steps
- Replace the gas cap as a first step ($15–$35)
- Scan for all codes and freeze frame data
- Locate the vent control valve near the charcoal canister at the rear
- Inspect the connector for corrosion and damage
- Test vent valve resistance
- Apply 12V — verify the valve clicks
- Check wiring from the valve to the ECM for damage
Cost Breakdown
- Vent control valve: $140–$300
- Wiring/connector repair: $85–$275
- Purge solenoid: $80–$210
- Charcoal canister: $155–$340
- Diagnostic fee: $80–$140
Can I Drive With P0446?
Yes. P0446 is an emissions code. Your Ascent's 260-hp turbo boxer, CVT, AWD, and towing capacity are unaffected.
Warranty and DIY
Your 2020 Ascent 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 under the rear of this large SUV.