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Bob, Auto Tech
Category: Chevy
Satisfied Customers: 4087
Experience:  Plus 40 years GM, over 30 certified with Chevrolet, ASE certified Master Tech. (Expired, Retired)
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I have a 2003 chevy cavalier with code p0440. i changed the

Customer Question

I have a 2003 chevy cavalier with code p0440. i changed the gas cap and it dident do nothing for the problem can you help??
Submitted: 8 years ago.
Category: Chevy
Expert:  Bob replied 8 years ago.
Unfortunately there are a lot of different components that can set this code. Any time the evaporative part of the emission system will not hold a vacuum or has a leak this code is set. Many times by a loose gas cap. But there are also many other reasons for it. About all you can do at home would be to check the system for broken or unhooked vacuum lines at the evaporation canister, the purge and vent valves, etc. Any time one of these valves fails to open or close at the correct time, it lets the system leak vacuum, same thing happens if a hose is broken or the seal around the fuel tank pressure valve or sending unit is bad. The only way to test the system for malfunctioning components is with a class 2 scanner like the one the dealers use. With the scanner, the system can be function tested to see what valves or solenoids are or are not working and they can be turned off and on remotely with the scanner. A regular code reader can't do these function tests, only a class 2 scanner because of the type of system it is. If none of the valves fail any of the tests, then the system has to be connected to a special tester that the dealers use to fill the system with smoke so they can determine where the leak is and then do repairs. The other thing to remembers is that the warranty on some of the emissions systems parts is 5 years or 80,000 miles, so some or all of it may still be covered by the factory. A call to the dealer will find out for you. Thanks