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What care are we talking about?
P0440 is Evaporative Emission Control.
This indicates that a part of the EVAP control system is no longer fuctioning correctly. The EVAP system consists of many parts, including (but not limited to) the gas cap, fuel lines, carbon canister, purge valve, and other hoses. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle’s fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.
Possible Issues
The gas cap is not installed or working properly
The purge solenoid has failed
The canister is plugged and not working properly+1 on Grayfox’s post except that code does not usually represent a gas cap problem, it means that something in the evaporative emission system is not working properly, normally they make troubleshooting flow charts in the service manual that will help you
We really need to know what year make and model this vehicle is to help you a little more. Sooo many possibilities on what could be the cause
Quoted From mrgmguy:
its a 99 BUICK CENTURY 3.1L before it said p0442 then after about 2-3 months it went to p0440
I ALSO HAD THIS CODE COME UP ON MY 69 BUICK SKYLARK TURNED OUT IT WAS JUST THE GAS CAP BUT THIS CENTURY HAS ME STUMPED
P0440
Remove and reinstall the gas cap, clear the code, and drive for a day and see if the codes come back.
Inspect the EVAP system for cuts/holes in tubes/hoses
Inspect for damaged or disconnected hoses around the Evap purge solenoid
Check the sensor
Check the purge valve
Lastly I would use a smoke machine to detect leaks. They make it really easy to pinpoint the smallest leak.One last thought.. “GM has reported some issues with spiders building nests in the vent solenoid which prevents it from sealing properly.”. “They
What does your fuel fill pipe look like? If it is all rusted and scaley, this is probably you source of the problem. Also, how does does the gas tank look, same thing as the fuel fill pipe. The hole doesn’t have to be rig to make a vacume leak. Also, check your gas cap O-Ring that seals against the filler neck, if you see ANY cracks, replace it.
The best way to diagnose emission related codes is with a smoke machine as already stated and a bi-direction scan tool that can activate the purge control solenoid and vent valves.
I got that code with bad vapor canister with my car. I got it used and the previous owner was over filling the gas tank.
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