2001 sonama P0440

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

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.

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

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

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.

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

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

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?

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

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

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

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.

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.

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?

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.

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.

same code yeah and time dont really matter i just wanna save money i dont smell any fuel but ill check anyways and how do you check the vent valve and plurge solenoid and pressure sensor??? do i look at hoses first or that first the purge solenoid has been changed once already i looked in the service records if that means anything

same code yeah and time dont really matter i just wanna save money i dont smell any fuel but ill check anyways and how do you check the vent valve and plurge solenoid and pressure sensor??? do i look at hoses first or that first the purge solenoid has been changed once already i looked in the service records if that means anything

Doe the system have and hold vacuum?
If you have a vacuum leak on the system you need to look for and check that first.
Testing requires good equipment and repair knowledge.
A lot of the testing requires a good engine capable scanner to start with.
Also a good repair flow chart for that code.
Which can be found in a factory repair manual or a All Data DIY sub.
http://www.alldata.com/products/diy/index.html

If you do not have them better find a good repair shop that does.

how do you test for vaccum? and i dont have any of that stuff just a matco code reader so your saying im best off to take it to a shop with a smoke machine and other testers? wat if its somethin simple like a hose should i not drop the canister and check that?

how do you test for vaccum? and i dont have any of that stuff just a matco code reader so your saying im best off to take it to a shop with a smoke machine and other testers? wat if its somethin simple like a hose should i not drop the canister and check that?

To test for vacuum hook up a vacuum gauge to it and see what you got.

Let us know if it has vacuum and if vacuum holds.

where do i hook the vacuum gauge up to? and wat do they look like i know i dont have one but maybe one of the mechanics i know have one i can borrow

You will need to hook it up any place on a line or fitting that should tank vacuum on it.

If you do not know what one looks like you had better get one of the mechanics to look at it.

Or Better yet get this for your truck.
http://www.alldata.com/products/diy/index.html

ok i got a vaccum guage i know wat you mean know so a line off the canister or under the hood somewhere where is best?

ok i got a vaccum guage i know wat you mean know so a line off the canister or under the hood somewhere where is best?

Any place on the evpa system that should have tank vacuum on it that you can hook up the gauge to.
Get a all data sub and look for the evpa tank vacuum system and lines.

i got the diagram in the manual i have ill hook the tester up this weekend and check how much vaccum should i have if there is no leaks?

i got the diagram in the manual i have ill hook the tester up this weekend and check how much vaccum should i have if there is no leaks?

I do not think it should range over 4.5-5 in vacuum at the most.

Let us know what yiou get and if any leaks.

EVAP vacuum is measured in inches of water, not mercury, BIG difference. Inches of water is far more accurate, 1 inch of mercury equals approximately 13.595 inches of water. Like MT said, better have a qualified technician look at it.

ive left it for a while but starting to notice a fuel smell when i turn corners and stop??? wat does this mean