Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P0446: EVAP Vent System Performance: Description
This DTC tests Evaporative (EVAP) emission system for a restricted or blocked EVAP vent path. Powertrain Control Module (PCM) commands EVAP canister purge valve on and EVAP canister vent valve on. This allows a vacuum to be applied to EVAP system. Once a calibrated vacuum level has been reached, PCM commands EVAP canister purge valve off and EVAP canister vent valve off. PCM monitors Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. DTC sets when vacuum does not decrease to about zero in. H2O in a calibrated time.
For the relationship between the on and off states, and the open or closed states of the EVAP canister purge and vent valves, see EVAP VALVE LOGIC table under DTC P0440: EVAP SYSTEM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.