Decoding P0446 on Your 2020 BMW 3 Series
A P0446 code on your 2020 BMW 3 Series (G20) indicates an EVAP vent control circuit malfunction. The DME has flagged a fault in the fuel tank vent valve (FTVV) circuit. The G20 was BMW's first full year of the seventh-generation 3 Series, with the B48 2.0L turbo in the 330i and B58 3.0L turbo in the M340i.
At five to six years old, your BMW is past the 4-year/50,000-mile basic warranty but still well within the federal emissions warranty window. BMW's plastic EVAP components begin showing age-related wear around this mileage.
Symptoms Uncovered
- Check engine light on with P0446 stored in DME
- Fuel nozzle shutting off during fill-ups
- EVAP readiness monitor incomplete
- May appear alongside P0441 or P0456
Most Likely Causes
- Fuel Tank Vent Valve (FTVV) Wear (High Likelihood): BMW's plastic FTVV is known to degrade with age. After five-plus years, the internal solenoid seal hardens and the valve fails to operate properly. Parts $80–$170, labor $115–$235.
- FTVV Connector Corrosion (High Likelihood): Five years of road exposure degrades the underbody connector. Salt, moisture, and temperature cycling cause pin corrosion. Repair costs $65–$155.
- Leak Diagnosis Pump (LDP) Failure (Medium Likelihood): The electric LDP can wear after years of use. A failing pump affects EVAP system monitoring accuracy. Parts $105–$225, labor $125–$260.
- EVAP Line or Hose Deterioration (Medium Likelihood): BMW's plastic and rubber EVAP lines become brittle with age and heat cycling. Cracks or loose connections develop. Repair costs $80–$240.
- Charcoal Canister Cracking (Low Likelihood): BMW's plastic canister housing can develop micro-cracks from thermal cycling. More common on higher-mileage vehicles. Parts $160–$345, labor $130–$265.
Investigation Steps
- Scan DME for all codes and freeze frame data using ISTA+ or compatible scanner
- Inspect FTVV valve and connector — check for physical damage and corrosion
- Test FTVV solenoid resistance and operation
- Test LDP pump function
- Inspect EVAP lines and hoses for cracks or brittleness
- Smoke test the system to locate any physical leaks
Repair Costs
- Fuel tank vent valve: $195–$405
- Connector repair: $65–$155
- Leak diagnosis pump: $230–$485
- EVAP line repair: $80–$240
- Diagnostic fee: $150–$220
Driving With P0446
P0446 won't affect your 3 Series' performance. Whether you drive a 330i (255 hp) or M340i (382 hp), engine power, the ZF 8-speed automatic, and xDrive AWD all operate normally.
Emissions Warranty
Your 2020 3 Series is past BMW's 4-year/50,000-mile warranty. However, the federal emissions warranty covers EVAP components for 8 years/80,000 miles through 2028. Contact your BMW dealer to check eligibility based on mileage.