Automakers created the evaporative emission control system to keep the fuel vapors in the fuel tank at bay. After you pump gasoline into your fuel tank, it will sit there for a while until your engine needs to use it. During that time, fuel vapors in the tank try to make their way into the atmosphere. The EVAP system stops that from happening in order to protect the environment and increase the fuel efficiency of your vehicle.
During this process, the engine control module opens the vent control valve to allow the vapors to go into a vent line that leads to the charcoal canister. The charcoal pellets of the canister absorb the fuel vapors and store them for safekeeping. When the engine demands the vapors, the purge volume control valve allows the proper amount of vapor to pass into the intake manifold. The vapors are mixed with the air and fuel combination right before combustion occurs in the engine cylinders.
If you ever smell fuel vapor and see the Check Engine warning light come on at the same time, then you might have a leak in your fuel tank or charcoal canister. There could also be a problem with your canister vent control valve or purge volume valve. Perhaps you have a loose fuel cap or an EVAP hose that is leaking.
To verify whether you have an EVAP system malfunction, do a diagnostic scan on your engine control module to see which diagnostic code they give you. If you see P0440 on the display screen, then you have an EVAP system malfunction due to one of the reasons just mentioned.
This is not a severe problem in the beginning because you won’t have any driving problems. But if you have your vehicle undergo an emissions test, it will ultimately fail the test. That could be a problem if you live in a state which requires vehicles to pass these tests every year. Furthermore, the components of your EVAP system might suffer further damage if you procrastinate on fixing the problem.
- P0401: Exhaust EGR Flow Insufficient
- P0446 Evaporative Emission Control System Vent Control Circuit Malfunction
- P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
Just to be safe, you should have a professional auto technician repair the faulty components or parts that caused trouble code P0440 to come up in the first place.