Leaking gas cap

the most common causes are vent solenoid and fuel cap
P0440 PONTIAC code possible causes

• Missing or loose fuel cap
• Incorrect fuel filler cap used
• Fuel filler cap remains open or fails to close
• Foreign matter caught in fuel filler cap
• EVAP canister or fuel tank leaks
• EVAP system hose leaking
• Fuel tank leaking
• Faulty vent solenoid
• Faulty EVAP purge switch

https://www.justanswer.com/pontiac/9xoy3-2000-pontiac-montana-3-4l-check-engine-light-p0440.html

https://www.yourmechanic.com/article/p0449-obd-ii-trouble-code-evaporative-emission-control-system-vent-valve-solenoid-circuit-malfunction-by-spencer-clayton

Call for service now. You don't want to mess with leaking gas.

First thing, make sure your gas cap is on tight. And that you are not overfilling the car at the station or spilling gas. Assuming you have checked that,

The main causes of gas odor are flooding when starting, a leaking oil filler cap, broken or leaking spark plugs, or a leak in the gas tank/filler/fuel lines. That's the one you should be worried about. I had a car with a cracked gas filler, gas pooled on top of the tank and later caught on fire: the car was completely engulfed within 45 seconds and i was lucky to get out alive.

https://www.yourmechanic.com/article/is-it-safe-to-drive-with-a-gas-leak

https://www.carbibles.com/gas-smell-in-car/

A loose gas cap or bad gas cap can cause this ,or filling gas tank while it running .or it could be a small leak in the evap system

Trouble Code: P0442
Most likely the gas cap.Hope this helps. Randy
EVAP Control System Small Leak Detected
Possible Causes:


Canister Purge valve is damaged, leaking or it has failed Charcoal canister is loaded with fuel or moisture Fuel filler cap loose, cross-threaded, incorrect part or damaged Fuel tank is cracked (leaking), or a leak exists in the 'O' ring Fuel tank pressure sensor is damaged or has failed Fuel vapor line(s), fuel pipes or hoses damaged or leaking PCM has failed

this is a evaperativ emissons code on newer vehic when filling up the tank if you round off dollars your corcoal canester is bad it is safe to stop pumping gas when the pump stops if you dont round dollars you should also check gas cap seal and make sure you click it three time when tighting if this dose not help you might have have a small leak in the tank seals or a bad purge vavle

You cant escape some fuel leak. To get the least amount of leak, Let sit overnite without running, Then replace, No special tool should be required

This indicates a fuel vapor leak in the EVAP control system. It means a very small leak has been detected. In fact, the leak can be from a hole as small as 0.04" in diameter. 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.
code P0442 most likely means one or more of the following has happened:

• A loose or improperly affixed gas cap
• A non-conforming gas cap (i.e. not factory/original brand)
• A small leak/hole in a fuel vapor hose/tube
• Other small leak in EVAP system
• Faulty vent o-ring seal

With a P0442, the most common repair is to:

• Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
• Otherwise, replace the gas cap, or
• Inspect the EVAP system for cuts/holes in tubes/hoses

means small evaporative emmisions leak. there is a vapor leak in the fuel system, either a bad or loose gas cap, cracked filler neck etc. id try the cap first, if not that you can fix yourself. a shop will pressurize the system with nitrogen and smoke and locate the leak in this manner. good luck

It sounds like the return fuel line is leaking. There are two fuel line and one is the high pressure line which goes to the fuel pressure regulator then to the fuel rails. There is then a return line from the fuel rail to the gas tank.
With the amount of fuel leak, it's going to be the return line since it's not that bad compared to the high pressure side. Follow the fuel lines from the drivers side around the steering shaft to the engine. The high side and low side (return) run side by side and you should see it leaking when the engine is running.
Good luck and hope this helps.

P0456 is a code set when there is a very small leak (theres very small leak, small leak and a couple of others, your code indicates the smallest level of leaking). This can be caused by a vacuum line that is cracked or otherwise leaking on the evaporative (EVAP) system. It could even be from a gas cap that is not sealing properly, though typically a gas cap leak tends to set code P0441. Just the same, and since it is the cheaper way to go, start by replacing the gas cap and see if that clears the code and any check engine light you may have.

Once you replace the gas cap you may need to disconnect the battery for a couple minutes to reset everything if you dont have access to a scanner that can do it.