Safe to drive. Repair to pass emissions and extinguish the MIL. P0446 means the PCM has detected a problem with the electrical circuit that operates the EVAP canister vent valve (vent control solenoid) — not a fuel-vapour leak, but a circuit or component fault in the vent side of the EVAP system.
What P0446 means
The EVAP system traps fuel vapour from the fuel tank in a charcoal canister and periodically purges that vapour into the intake manifold. To run an EVAP leak test, the PCM must close the vent valve — sealing the fresh-air port on the canister — while simultaneously opening the purge solenoid to draw vacuum through the sealed system. P0446 is stored when the PCM cannot control the vent valve's electrical circuit as expected: the circuit is open (broken wire, corroded connector, dead solenoid coil) or shorted, so the valve either cannot be commanded closed or the PCM sees an electrical anomaly on the control line. Unlike P0440 or P0455, this code is about the wiring and solenoid, not a hole in the vapour path.
Symptoms
- Check engine light on with P0446 stored — often the only detectable symptom
- EVAP readiness monitor will not complete, causing the vehicle to fail or be unable to complete an emissions test
- Occasionally, a faint fuel vapour smell if the vent valve is stuck open and the canister cannot hold vapour
- Fuel tank may be slow to fill or make unusual pressure sounds if the vent is stuck closed
Common causes
- Failed canister vent solenoid (CVS) — the coil has opened internally, drawing no current, or has shorted — the most common hardware fault
- Corroded or water-intruded connector at the vent valve, which is typically mounted under the vehicle near the fuel tank and exposed to road spray
- Open or high-resistance wiring between the PCM and the vent valve — road salt, heat, and chafing against frame rails are common causes on trucks
- Rodent-damaged wiring in the harness running to the rear undercarriage
- PCM driver circuit fault — rare; only suspected after all external wiring and the valve itself test good
Severity & driving advice
Severity: Low — P0446 rarely affects drivability but blocks the EVAP monitor and guarantees an emissions test failure until repaired.
Can I drive? Safe to drive. Repair to pass emissions and extinguish the MIL.
Diagnostic approach
- Confirm the fault is circuit-based, not a companion leak code — Scan all EVAP-related codes. If P0440, P0441, P0455, or P0456 are stored alongside P0446, the vent circuit fault may be preventing the EVAP system from sealing — the vent valve must close for the leak test to run. Fix P0446 first; the leak codes may clear once the vent circuit is functional.
- Locate and inspect the vent valve and its connector — The canister vent solenoid is typically mounted near the charcoal canister, which on most trucks and SUVs is under the rear of the vehicle near the fuel tank. Raise the vehicle safely and inspect the valve's two-wire connector for green corrosion, backed-out terminals, or water ingress. On GM trucks, the vent solenoid and its connector are known to corrode from road spray — the connector is often the fault before the valve itself fails.
- Measure the vent solenoid coil resistance — Unplug the vent valve connector and measure resistance across the solenoid's two terminals. A healthy solenoid typically reads in the range of 20–40 Ω (confirm specification for your specific vehicle). Open circuit (infinite resistance) confirms the coil has failed internally. Near-zero resistance indicates an internal short. Either result warrants replacing the solenoid.
- Verify wiring continuity and PCM control signal — If the solenoid resistance is within specification, test the wiring: check for battery voltage at one terminal and PCM-switched ground at the other when the valve is commanded on (use a scan tool with bi-directional controls to command the vent valve). High resistance in the supply or control wire — which may not be obvious on a static voltage check — shows up under current flow as a voltage drop. Repair or replace corroded sections before suspecting the PCM.
Make & model notes
General Motors: GM trucks and SUVs (Silverado, Suburban, Tahoe, Yukon) are the most common P0446 vehicles. The vent solenoid mounts near the fuel tank in the full spray path of the rear axle; connector corrosion is the leading cause. Replacement vent valves are inexpensive (under $40) and accessible with basic hand tools.
Toyota: Toyota uses a Vapor Switching Valve (VSV) near the charcoal canister. P0446 on Camry, Tacoma, and 4Runner is often caused by moisture in the VSV connector or debris lodging in the valve body rather than electrical failure. Inspect the connector and valve before replacing.
Nissan: Nissan models including Altima, Pathfinder, and Frontier develop P0446 from the canister vent control valve failing near the fuel tank. Inspect the harness routing along the frame rail for chafing, as the harness run to the rear of the vehicle is long and exposed to road hazards on these platforms.
FAQ
Is P0446 the same as a fuel vapour leak?
No. Leak codes (P0440, P0455, P0456) indicate the system failed a pressure or vacuum test due to a hole or open path. P0446 is a circuit fault — the vent valve's electrical circuit is not operating as expected. You can have P0446 with a perfectly intact vapour system.
Can I clear P0446 and just keep driving?
Yes for short-term safety, but the code will return on the next complete drive cycle. The EVAP monitor will not pass with P0446 active, so the vehicle cannot complete an emissions test. The check engine light will stay on.
My P0446 came back after replacing the vent valve — what now?
If a new valve did not fix it, the fault is in the wiring or connector — not the valve. Trace the two-wire harness from the valve to the PCM, check for damaged insulation, and perform a voltage-drop test under load. Connector corrosion can appear clean visually but still add enough resistance to fail the circuit test.
Does P0446 affect fuel economy or engine performance?
Generally no. The vent valve only operates during the EVAP leak test, which runs once per drive cycle under specific conditions. A stuck-open vent valve will prevent the test from completing but will not noticeably affect how the engine runs.