2001 sonama P0440

[luxeryvic]

hi i just got the code P0440 evap system, where do i start what commonly causes this???

[MT-2500]

Originally Posted by luxeryvic

hi i just got the code P0440 evap system, where do i start what commonly causes this???

Code 440 is evap emmision system is unable to pull vacumn on fuel tank.
Most commoon problems are.
Bad gas cap.
People leaving it off or filling up with engine running.

[luxeryvic]

ok well its on i checked that i have the service records from the person who had it before me and this code was on before and the purge solenoid was replaced and when i hooked up my code reader it showed this code twice does that mean the solenoid? or could it still be the gas cap? also the truck has 251000 km and the charcoal canister doesnt look like it has been touched and nothin bout the pressure sensor either??? wat do i start with or try

[luxeryvic]

i did fill up before this came on, could possible over filling cause this? purge valve maybe?

[MT-2500]

Originally Posted by luxeryvic

i did fill up before this came on, could possible over filling cause this? purge valve maybe?

Code says you have a vacumn leak.
Find out where it is losing vacumn.

[luxeryvic]

ok how do i find where the leak is with out a smoke machine?

[luxeryvic]

also if i dont find a leak wat do i do then?

[MT-2500]

Originally Posted by luxeryvic

ok how do i find where the leak is with out a smoke machine?

You pull a vacumn on tank and the look for vacumn leaks.
Have you made sure gas cap is good and sealing?
Has codes been cleared and returned?

[MT-2500]

Originally Posted by luxeryvic

also if i dont find a leak wat do i do then?

Check and make sure it is leaking or not holding vacumn.

[luxeryvic]

wat do you mean by You pull a vacumn on tank and the look for vacumn leaks.?

and the cap seems to be going on alright but ill chesk the gasket and ill try replacing the cap first i looked around at the hoses and didnt see anythin noticable

[MT-2500]

Start it up and run the engine.
And see if it pulls vacumn and holds vacumn on fuel tank.

First thing I do is go to the GM dealer aand get a GM gas cap.
Install it and clear code and see if it comes back.
May take 2 to 3 hundred miles forcode to reset if it is going to come back.
No code come back problem is fixed.
If code comes back you will need to find the vacumn leak.

Good luck and let us know how it goes.

[MT-2500]

You can not tell if a gas cap is bad by looking at it.
Unless someone has a cap tester relplace it and see if that fixes the problem and most caps require 3 clicks to tighten them.
Also look for rusted or dirty or pitted gas filler neck.

[luxeryvic]

ok so i put the new gas cap on cleared the code and drove but it just came back on wat next? drop the canister and check hoses for cracks?

[MT-2500]

Originally Posted by luxeryvic

ok so i put the new gas cap on cleared the code and drove but it just came back on wat next? drop the canister and check hoses for cracks?

Same code no?
Look for and check for vacumn leak.
Make sure vent valve and plurge solenoid and pressure sensor is working good.

[Mark1950]

Listen to MT-2500 – the man is wise.

Unless you want to waste a lot of time chasing the cause of the P440 code – a smoke test is the only way to go.

I spent a year looking for the same type of problem on my 99 Sonoma and it turned out to be the filler neck –

Do you have gas fume smell gas coming from the behind the filler door?

You may need to remove the filler neck to see if it’s rusted – look at the neck that goes into the rubber hose – mine rusted in an area that you could not see unless it was removed from the truck.