Fault codeP0446

MODERATE

Evaporative Emission Control System Vent Control Circuit Malfunction

What this code means

Evaporative Emission Control System Vent Control Circuit Malfunction.

P0446 is a generic code: it means the same thing on every make. P0446 belongs to family P04xx — Emission controls. Its page explains how to read a code and groups all its codes by part.

Fuel vapour recovery (EVAP)

The EVAP system traps fuel vapour from the tank in a charcoal canister, then burns it in the engine through a purge valve. A vent valve and a pressure sensor let the control unit test the system for leaks, often after the car has been parked.

Symptoms

No driving symptom. In some cases the tank fills badly: the pump at the station keeps clicking off because air can no longer escape. The control unit found the canister vent solenoid not responding or its passage blocked.

Common causes

Vent solenoid seized or burnt out
Vent line blocked by dust, cobwebs or insects
Canister saturated or clogged
Corroded solenoid wiring or connector — it is often exposed under the car
EVAP circuit fuse or relay

How to diagnose it

Locate the vent solenoid, usually near the canister under the rear of the car. Check its connector: corrosion is common there. Feed it 12 V directly: it should click sharply.

If it works, follow the vent line to its end and check it is not blocked. Some models have a vent filter that can be replaced.

Watch it live in Klaro

With an OBD2 adapter plugged in, these live readings show the part at work, when your car reports them:

Commanded evaporative purge
Evap system vapor pressure
Fuel level

What to do

Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.

Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →

Repair cost

Solenoid: €30 to €120 for the part. Cleaning the line: free or nearly. Canister: €80 to €300.

How to read this code

PPowertrain
0standardised code
4Emission controls
46P0446