Emission controls · Powertrain · generic (SAE-defined)
P0446: Evaporative Emission System Vent Control Circuit
P0446 means the engine computer found a problem with the evaporative emission (EVAP) canister vent valve or its control circuit, which seals the system for leak testing.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0446 sets
The powertrain control module (PCM) commands the canister vent valve closed during EVAP testing and open during normal operation. It monitors the circuit electrically and may also watch tank pressure to confirm the valve actually opens and closes. If the circuit or the expected pressure response is wrong, it sets P0446. Some manufacturers define P0446 as a circuit fault and others as a performance fault.
Common causes of P0446
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Failed canister vent valve or solenoid
- Vent valve clogged by dirt, debris, or spider webs
- Blocked vent filter or vent hose
- Damaged wiring or connector at the vent valve
- Saturated charcoal canister blocking the vent path
P0446 symptoms
- Check engine light on
- Difficulty refueling, with the nozzle shutting off early
- Possible fuel odor
- Usually no drivability symptoms
How P0446 is diagnosed
- Scan for other EVAP codes and review freeze frame data
- Locate the vent valve, usually near the canister by the fuel tank, and inspect for debris and road damage
- Check the connector and wiring for corrosion
- Measure vent solenoid resistance and verify power and ground
- Command the vent valve closed and open with a scan tool and verify it seals and releases
- Check the vent hose and filter for blockage
Typical fixes for P0446
- Replace the canister vent valve
- Clean or replace a blocked vent filter or hose
- Repair wiring or connector damage
- Replace a saturated canister
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
Definitions can vary by manufacturer; check factory service information. Commonly reported on GM trucks and SUVs where the vent solenoid sits near the fuel tank.
Related codes & warning lights
P0446 FAQ
What does code P0446 mean?
P0446 means the engine computer found a problem with the evaporative emission (EVAP) canister vent valve or its control circuit, which seals the system for leak testing. The standard definition is "Evaporative Emission System Vent Control Circuit."
Can I drive with a P0446 code?
Yes, for normal driving. Some vehicles may be hard to refuel if the vent valve is stuck closed, with the pump nozzle clicking off repeatedly, so repair it soon.
Why is it hard to fill my tank with P0446?
If the vent valve is stuck closed, air displaced by incoming fuel cannot escape properly, which causes the pump nozzle to shut off repeatedly.
Why do vent valves fail?
They are often mounted underneath the vehicle where water, dirt, and road salt can corrode the valve or block its vent.
Keep researching
More emission controls codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.