Investigating P0446 on Your 2022 GMC Terrain
A P0446 code on your 2022 GMC Terrain points to an EVAP vent control circuit malfunction. The Terrain uses a 1.5L turbocharged four-cylinder and GM's standard EVAP architecture with a vent valve solenoid controlled by the ECM. On GM vehicles, P0449 frequently accompanies P0446 as a companion code targeting the same vent valve solenoid circuit.
With the basic warranty (3yr/36k) likely expired, your Terrain still falls within the federal emissions warranty (8yr/80k miles) covering EVAP components. Check your mileage to confirm coverage before paying out of pocket.
Clues and Symptoms
- Check engine light illuminated with P0446 stored
- P0449 companion code may also be present
- Difficulty at the fuel pump (slow fill or shutoff)
- EVAP readiness monitor not completing
Top Suspects
- Vent Valve Solenoid Failure (High Likelihood): The GM vent valve solenoid is the primary P0446 culprit. On the Terrain, it's mounted near the charcoal canister under the vehicle. Replacement runs $120–$220 installed.
- Vent Valve Wiring or Connector (High Likelihood): Corrosion or damage to the solenoid connector or harness causes circuit faults without a mechanical failure. Repair costs $80–$180.
- Purge Solenoid Valve (Medium Likelihood): A stuck purge valve disrupts EVAP system flow and can trigger P0446. Replacement is $100–$200.
- Charcoal Canister Saturation (Medium Likelihood): Overfilling fuel or canister age leads to saturation affecting the vent circuit. Canister replacement costs $200–$350.
- EVAP Line Damage (Low Likelihood): Cracked or disconnected hoses between components. Repair is $50–$150.
How to Investigate
Start by scanning for all stored and pending codes—P0449 alongside P0446 strongly points to the vent valve solenoid. Check the solenoid connector for corrosion and test the valve with 12V applied directly. A GM GDS2 scan provides enhanced diagnostics including solenoid command tests. VCDS is not applicable here—this is a GM vehicle.
Warranty and Cost
Your 2022 Terrain's basic warranty is likely expired, but the federal emissions warranty (8 years/80,000 miles) covers EVAP components through 2030. If under 80k miles, have a GM dealer handle this at no cost. Out of pocket, expect $120–$350 depending on the root cause.
Safe to Drive?
Yes. P0446 is an emissions circuit code that doesn't affect your Terrain's engine performance, transmission, AWD system, or safety features.