Faulty or stuck EVAP vent valve (solenoid); Blocked, pinched or contaminated vent line, filter or vent port (dirt, water, insects, mud); Damaged wiring, corrosion or poor connection at the vent valve connector; Saturated or damaged charcoal canister restricting airflow; Fault with the vent valve circuit in the engine control unit, such as a failed driver; Fuel tank pressure sensor fault giving misleading readings during the vent test.

P0446

EVAP System Vent Control Circuit.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
46: FaultThe specific fault in that area

What it means

P0446 is the generic code for a fault in the evaporative emission (EVAP) system vent control circuit. The engine control unit monitors the vent valve, which opens the charcoal canister to fresh air, and sets the code when the valve's operation or response does not match what it commanded. The cause is often electrical, but a stuck vent valve or a blocked vent path can also set it, and the exact layout varies by model.

Symptoms

Malfunction indicator lamp on
Difficulty refuelling, with the pump clicking off repeatedly
Fuel smell around the car or near the fuel tank
Failed emissions test or readiness monitor for EVAP not completing
Usually no change in how the engine runs

Possible causes

Faulty or stuck EVAP vent valve (solenoid)likely
Blocked, pinched or contaminated vent line, filter or vent port (dirt, water, insects, mud)likely
Damaged wiring, corrosion or poor connection at the vent valve connectorpossible
Saturated or damaged charcoal canister restricting airflowpossible
Fault with the vent valve circuit in the engine control unit, such as a failed driverrare
Fuel tank pressure sensor fault giving misleading readings during the vent testrare

How to diagnose

Read the stored codes and freeze frame data, and note any other EVAP codes such as P0440, P0442, P0455 or P0456 that point to the same fault
Visually inspect the vent valve, its connector, wiring and the vent hoses for damage, corrosion, water ingress or kinks
Check the vent port, filter and pipework for blockages, dirt or debris, as the position varies by model
Command the vent valve on and off with a scan tool that supports bidirectional tests, and listen for a click or watch for a change in tank pressure
Check the vent valve for a supply voltage and a switched signal from the control unit, and test the wiring for continuity and shorts to earth or voltage
Measure the vent valve coil resistance and compare it with the manufacturer specification for that model
Check the canister for fuel saturation or damage, and look for signs of overfilling the tank
Check the fuel tank pressure sensor readings against the expected values with the engine off, following the manufacturer procedure

How to fix

Replace the EVAP vent valve if it is stuck or the coil is out of specification
Clear any blockage in the vent line, filter or port, and replace any damaged pipes or hoses
Repair or replace damaged wiring and clean or renew corroded connector terminals
Replace the charcoal canister if it is saturated, blocked or cracked
Replace the fuel tank pressure sensor if it is proven faulty
Clear the code after the repair and confirm it does not return over a full drive cycle that completes the EVAP monitor

Can I keep driving?

Low severity

The car is normally safe to drive and the fault rarely affects performance. Book it in soon, as it can cause refuelling problems, fuel vapour smells and an emissions test failure.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.