P0446: Evaporative Emission System Vent Control Circuit
The engine computer sees a problem with the EVAP vent valve circuit, the valve that lets fresh air into the charcoal canister.
What P0446 means
The vent valve sits at the fresh air end of the charcoal canister. Normally open, it lets air in so vapors can be purged and so the tank can breathe while you refuel. During the EVAP self test, the computer closes it to seal the system. RepairPal explains that P0446 indicates an improper voltage drop in the vent valve circuit, which can be caused by too little or too much electrical resistance, so the code points to the solenoid coil and wiring as well as a stuck valve. Because the vent valve lives under the car, it often gets packed with dirt or corroded. A blocked vent can make it hard to fill the tank, because displaced air cannot escape, and the gas pump nozzle keeps clicking off. KBB suggests checking the gas cap first when the light comes on. Shops command the vent valve with a scan tool, check its resistance and power, and inspect the vent hose and filter for blockage.
Common symptoms
- Check engine light on
- Hard to fill the tank, with the pump clicking off early
- Fuel smell in some cases
- Usually no driveability change
- May appear with other EVAP codes
Most common causes
- Failed EVAP vent valve or solenoid
- Vent valve clogged with dirt or debris
- Open or shorted vent valve wiring
- Corroded connector near the tank
- Blocked vent hose or filter
What to check yourself first
Find the vent valve, often near the charcoal canister close to the fuel tank. Check for dirt, mud or spider webs blocking the vent hose or filter. Inspect the connector, which sits in a dirty, wet area under the car.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace EVAP canister (includes vent valve on many cars) | $558-$643 | On many cars the vent valve mounts on or with the canister. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | RepairPal explains P0446 can come from too little or too much voltage in the vent circuit. |
| EVAP smoke test to find the leak | $61-$90 | A smoke test is the standard way to find EVAP leaks. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
Related repair guides
- Tundra in Limp Mode With Code P2440 or P2442? The Air Injection Pump Problem Explained
- Ram 1500 Ticking on Cold Start? Broken Exhaust Manifold Bolts, Repair Cost and What to Ask
Related codes
- P0449 Evaporative Emission System Vent Valve/Solenoid Circuit
- P0455 Evaporative Emission System Leak Detected (large leak)
- P0442 Evaporative Emission System Leak Detected (small leak)
- P0440 Evaporative Emission System
- P0451 Evaporative Emission System Pressure Sensor/Switch Range/Performance