Emission codes
P0446: evaporative emission vent control circuit
The canister vent valve lets the fuel vapor system breathe fresh air, and closes so the system can be leak-tested. P0446 means that valve, or its circuit, is not doing what the computer asks.
P0446: can I drive, and what will the labor cost?
Estimated labor, replace the canister vent valve
$33 to $110
| Labor time (estimate) | 0.3 to 1 h |
| Rate used | $110/h |
| Technician wage, United States (average) | $27.13/h |
| Low: fix when convenient Safe to drive; if the pump clicks off early when refueling, the vent is likely blocked. | |
Labor only: parts and the diagnostic fee are not included. Hours are our estimate for a typical car; book times vary by model. Wage: BLS, May 2025.
P0446 is the generic OBD-II code for "evaporative emission system vent control circuit". The vent valve sits at the fresh-air side of the charcoal canister, usually near the tank or under the rear of the car. Normally open, it lets air in when the engine purges stored vapor and lets air out as the tank fills. The computer closes it to seal the system for the leak test. P0446 is set when the electrical circuit is faulty, or, on many cars, when the system cannot be vented or sealed as expected. The most frequent cause is the valve itself, stuck or blocked by dirt, spider webs or insects nesting in its filter or opening. A canister flooded with liquid fuel, often after repeated topping off at the pump, comes next, followed by wiring or a corroded connector at the valve. It is safe to drive. A blocked vent can make the fuel pump nozzle click off early because the air in the tank cannot escape.
After the repair: when does the light go off?
Light off by itself after about
2 days
| Fault-free trips needed | 3 |
| Warm-up cycles before the code can be erased | 40 |
| Stored code gone after about | 40 days |
Federal rule for model years up to 2016 (40 CFR 86.1806-05); a misfire or fuel fault must also stay away under similar conditions. Clearing codes with a scanner also resets the readiness monitors an inspection checks.
Codes, rules and labor data checked by Radif Partners · Editorial policy · Method and sources
P0446 at a glance
| Code | P0446 |
| Standard description | Evaporative Emission System Vent Control Circuit |
| System | Evaporative emissions (EVAP) |
| Severity | Low: fix when convenient |
| Common symptoms | fuel pump nozzle clicks off early, hard to fill the tank |
The refueling clue
As fuel goes in, air and vapor have to leave the tank through the canister and out of the vent. If the vent is blocked, pressure builds and the nozzle's automatic shut-off trips again and again after a few seconds. Owners describe it as a tank that "won't take fuel". If that happens along with P0446, the vent path is almost certainly the problem.
Why not to top off
When the pump clicks off, the tank is full to the level the system was designed for. Adding more pushes liquid fuel into the canister, whose charcoal is meant only for vapor. A soaked canister restricts airflow, can damage the vent valve, and may need replacing, at 0.5 and 2 hours of labor. The simple habit of stopping at the first click avoids it.
Checking the valve
With a scan tool, a technician commands the vent closed and open and listens for the click, then checks the resistance and power supply. A valve full of debris can sometimes be cleaned, but replacement is more common. Where the valve has a dust filter or an opening near the frame, a cover or a relocation kit from the maker exists on some trucks. Related codes in the same system include P0440 and P0455; after the repair, the clearing counter on this page shows how many days the light may take to go off.
Likely causes of P0446, in order
| Cause | How often |
|---|---|
| Vent valve stuck or blocked by dirt or insects | most frequent |
| Canister flooded after overfilling the tank | frequent |
| Wiring or connector at the vent valve | frequent |
P0446 repairs and labor time
| Repair | Labor (estimate) | At $110/h |
|---|---|---|
| Replace the canister vent valve | 0.3 to 1 h | $33 to $110 |
| Replace charcoal canister | 0.5 to 2 h | $55 to $220 |