P0446 and your Nevada smog check

The vent valve is a small part with a big role: when it closes, the computer can seal the fuel vapor system and check it for leaks; when it opens, the canister can breathe. If the computer cannot control or confirm that valve, it sets P0446. The car drives the same, but the Reno smog check will not pass while the lamp is on.

At a glance

• P0446 in SAE J2012: Evaporative emission system vent control circuit.
• The vent valve opens and closes the canister to fresh air on the computer's command.
• Any lit check engine light fails 1996 and newer light-duty vehicles in Nevada (DMV).
• Test early in the 90-day window to leave time for a repair and retest.

The valve behind the code

SAE J2012 defines P0446 as "Evaporative emission system vent control circuit." In the EVAP system, fuel vapor from the tank is stored in a charcoal canister. A vent valve, usually near the canister, normally stays open so the canister can breathe. During a self-test the computer closes it to seal the system, then watches pressure or vacuum to look for leaks.

The code means something in that vent control is off: the valve may not respond, its electrical circuit may read wrong, or the system may not hold the condition the computer commanded. Because the leak test cannot run properly, the computer reports the fault.

Questions drivers ask first

Is it dangerous? Usually the car runs normally. Will it pass? Not with the lamp on. Can I just clear it? That leads to a not ready rejection, the DMV says, because the computer's self-checks reset. Those three answers shape everything else on this page.

One more: does the season matter? The rule does not change with the weather. A lit lamp fails in July and in January, and a passing test is good for 90 days whenever you take it.

Common causes a repair shop checks

Common causes a repair shop checks for P0446 include a vent valve that sticks or has failed electrically, a vent line or filter that is blocked by dirt or debris, damaged wiring or a corroded connector to the valve, and problems at the canister. Vent parts tend to sit low near the tank, where road dirt and winter slush collect. A loose gas cap can also upset EVAP tests, and the DMV lists a loose cap as a common reason the light comes on suddenly, so check it first.

Testing in Washoe County with this code

During the inspection the technician reads the VIN with a bar code reader and connects the analyzer cable to the diagnostic port; the DMV receives the result in real time. A lamp lit by P0446 makes it a fail.

That fail is not wasted. The DMV calls the failed test a legal document showing why the vehicle fails; it supports a ten-day movement permit at reduced cost if registration has expired and opens the waiver process if the repair gets costly. Repair spending before that first failed test cannot be counted toward a waiver.

A practical timeline

A passing test is valid for 90 days for a renewal, so testing early leaves time if something turns up. A reasonable order for an EVAP code looks like this.

• Check the gas cap and give the car a few days of normal driving.
• If the light stays on, test so you have the failed report, then take the car to a repair shop.
• After the repair, drive up to a week of mixed city and highway trips; the EVAP monitor can be one of the last to finish.
• Come back for the retest.

Waiver and emissions warranty notes

Nevada requires a repair and a passing second test to register. If the vehicle still fails after repairs, the Washoe waiver needs receipts of at least $200 in parts and labor at a 2G licensed authorized station, or at least $200 in parts bought by the owner within 14 days after the initial test, both tied to the failure. See the waiver page.

Before paying, ask the dealer about a recall or the federal emissions warranty, which covers some expensive emission components for up to 8 years or 80,000 miles. The DMV gives no waiver to a vehicle eligible for warranty coverage.