CEL light came on today...got DTC P0440. Said could be caused by fuel cap. I think its ok, also said yo check for fuel soaked canister. Is that the thing behind left rear bumper corner piece?
This 3rd or 4th time light came on and noticed that only came on ehrn almost at 1/8 fuel....could that have anything to do with it?

Thanx in advance!

 

P0440 is a fault in the EVAP system which covers a ton of things. Could be electrical, mechanical, or a physical leak somewhere from the filler cap to the purge solenoid on the engine, or anywhere inbetween. Yes, could be filler cap, purge canister, fuel filler neck, vapor lines, purge lines, tank pressure sensor, fuel tank, etc etc etc. The diagnostic flow chart is 4 pages in length making P0440 one of the most difficult and time consuming DTC's to troubleshoot, even for an experienced tech with all of the test equipment. The most common problems are faulty fuel cap, and if it's a 2 door, a rusted out filler neck.

 

I got the same code yesterday. Replaced the gas cap and still have CEL, so I guess I will keep looking.

So that I am clear, the CEL will clear itself when problem is corrected, right?

 

The "CONDITIONS FOR CLEARING THE DTC" paragraph explains: https://blazerforum.com/forum/diagno...plained-35145/

"Check for the following conditions" explains what can cause the DTC to set.

If you manually clear the codes, the check engine light will go off. The P0440 will not return unless/until the EVAP monitor runs its tests, completes them, and detects the failure.

 

Thanks Captain! I think I will just drive and monitor a while before I dive into all that other crap!

 

I replaced gas cap but not sure if it fits correctly. It clicks but doesnt get tight. Are they supposed to be that way.?

 

They get fairly tight and then make a ratchet like sound. Probably have the best luck with a Stant or OEM cap. Make sure the sealing surface on the filler neck is smooth, and no rust.

 

Thank s for the info!