P0446 Toyota Highlander
EVAP Vent Control Circuit Malfunction · Powertrain Code · Low · Repair: Moderate
What is P0446?
The EVAP vent control circuit has an electrical issue preventing proper vent valve operation.
When the Toyota Highlander triggers code P0446 (evap vent control circuit malfunction), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the Toyota Highlander.
This repair is rated moderate, meaning some experience and specialty tools required.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Toyota Highlander.
Common Causes on Toyota Highlander
- EVAP vent valve circuit malfunction — vent solenoid failed or stuck
- EVAP vent filter clogged with dirt or spider webs (common on Tacoma and 4Runner)
- Wiring issue to the EVAP vent valve solenoid
- Cracked EVAP vent hose near the canister
Symptoms
- Check Engine Light on
- Difficulty filling gas tank — pump nozzle clicks off repeatedly
- No driveability symptoms
- Failed emissions test
Notes for Toyota Highlander
On Toyota trucks (Tacoma, 4Runner, Tundra), spiders love to build nests in the EVAP vent filter — check this first, it is a well-known Toyota issue.