Signs of an Improperly Working Vent Solenoid

by Horacio GarciaUpdated July 12, 2023
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pumping gas image by Mat Hayward from

The vent solenoid electronically controls the Evaporator (EVAP) Emissions System by preventing gasoline fumes from being released into the atmosphere. The powertrain control module (PCM) monitors the build-up of gasoline fumes inside the fuel tank and throughout the fuel line. Once fumes build-up to a excessive level, the vent solenoid is engaged by the PCM.

Fault Code

The most common sign of an improperly working vent solenoid is a fault code being displayed on the dashboard or instrument panel. Depending on the vehicle's manufacturer, the fault code P1451 or check engine warning light will be displayed. The vehicle's owner can only determine if the vent solenoid is causing the fault code or warning light by taking it to an authorized technician and having the vehicle placed on a diagnosing scanner.

High Emission Test

A malfunctioning vent solenoid will emit unusually high emissions during testing. this is because gasoline fumes are not being sent through the vent solenoid. This build-up of fumes inside the fuel lines can also cause the vehicle to misfire or stall.

Leaking Vents

A malfunctioning vent solenoid can also be traced back to a leak in the system. A leak can allow air to get into the fuel lines, creating air pockets throughout the fuel system. The vehicle will then stall momentarily. The leak can be trace back to one of the fuel line hoses; as a result of the vent solenoid remaining slightly open; or a improperly tightened gas cap.

Engine Coughing or Choking

Another sign of a malfunctioning vent solenoid is when the vehicle's engine coughs or chokes during ignition. This ignition problem is caused by enough fuel entering the fuel lines. Gasoline fumes are typically stored and recycled in the EVAP canister. The vent solenoid then acts to prevent liquid fuel from entering the EVAP canister. A malfunctioning vent solenoid will allow liquid fuel into the EVAP canister, preventing a smooth flow of fuel into the engine during ignition.

Video: Symptoms and Diagnosis of a Bad Evap Vent Valve Solenoid

Helpful comments on this video:

  • If anyone is having trouble pumping gas in this model car, you definitely want to check the filter tube vent. This is located driver's side rear wheel well. You will have to remove the wheel to get access to the plastic shroud in the wheel well. The filter tube vent is located behind there. You'd be surprised how much road debris actually gets trapped up in there despite it being covered. When I cleaned mine, I removed a dustpan sized pile of dirt and sand. In my case, cleaning that filler vent did the trick allowing me to pump gas, and not have to do the "flip the gas nozzle upsidedown" trick in order to pump gas. 3 years since and still pumping gas fine. Just a quick tip no one really talks about.
  • Awesome detailed video! Exactly what I needed....I like the way you draw out diagrams and make them simple enough a simpleton like myself can comprehend...I had code P0449 and followed your instructions...I bench tested it with my power probe and get 12v on hot side and 0v green light negative on control side, however I don't get an audible click whatsoever when I supply 12+ v through my probe..I also used my bi- directional scan tool to help troubleshoot and test, still no click! I'm gonna buy a new vent solenoid.... thank you.

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