What P0446 means
P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 4, places it in the auxiliary emission controls subsystem; the last two digits identify the specific fault.
The vent valve sits near the charcoal canister and lets fresh air in or out of the EVAP system. The engine computer closes it to seal the system for leak tests. It is exposed to dirt and water on many vehicles.
What “Control Circuit” means here
A "control circuit" fault means the module's driver for the EVAP vent valve detected a problem on the wire it uses to command the component: an open, a short, or a voltage that does not match what it is commanding. This is an electrical fault, so the component, its connector and wiring, and its power feed are the places to look.
What you may notice
Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0446:
- Usually none
- Difficulty refuelling (pump nozzle clicking off) if the vent is blocked
- Fuel smell
Causes to consider
- Blocked EVAP vent valve
- Spider web/dirt clog in vent tube
- Corroded vent solenoid wire
Where to start diagnosing P0446
- Inspect the vent valve and its filter for dirt, water or spider webs.
- Check the connector and solenoid resistance.
- Command the valve closed with a scan tool and listen for it.
Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.
Live data to watch
These standard OBD2 values relate to P0446. Support varies by vehicle; a value your car does not report will simply be missing.
| Value | What to look for |
|---|---|
| EVAP system vapour pressure (PID 0x32) | Should change when the vent closes during a test. |
Related codes
Codes from the same EVAP vent valve family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.
| Code | Definition |
|---|---|
| P0447 | Evaporative Emission System Vent Control Circuit Open |
| P0448 | Evaporative Emission System Vent Control Circuit Shorted |
| P0449 | Evaporative Emission System Vent Valve/Solenoid Circuit |
| P0498 | Evaporative Emission System Vent Valve Control Circuit Low |
| P0499 | Evaporative Emission System Vent Valve Control Circuit High |
Further reading
Symptoms that lead to P0446
If you have not scanned the car yet, or P0446 is one of several codes stored, these guides start from what the vehicle is actually doing.
Frequently Asked Questions
What does P0446 mean?
P0446 is the generic SAE J2012 code for "Evaporative Emission System Vent Control Circuit Malfunction". In plain terms, it means the engine computer has detected a "control circuit" fault on the EVAP vent valve.
Can I keep driving with P0446?
Drivable; may affect refuelling and inspection readiness.
What should I check first for P0446?
Inspect the vent valve and its filter for dirt, water or spider webs.
Definition source: SAE J2012 / ISO 15031-6 generic DTC definitions. This is the generic meaning that applies across makes; a manufacturer can define a code more narrowly or add its own sub-codes, so confirm against the service information for your vehicle before replacing parts. Written by the OBDAssistant engineering team — see our editorial policy.