I've been trying to solve a code problem for sometime and I'm hoping someone out there will be able to help? It's a PO 446 and has to do with the fuel system. I've changed the fuel cap ( got a OEM type from the dealership) , changed the fuel sensor on the manifold ( can't think of the proper name just now), of course i"ve changed the filter AND was about to change the charcoal canister when the the parts guy, which I've known forever, said he's only sold maybe 4 or 5 in his 30+ years behind the counter and those were because of a wreck! I always reset or erased the code and within a day it's back, EXCEPT if I go on a trip (all highway driving) but when I return to city driving, BOOM, it's back !!!! The only other thing I see is the gas gauge acts like the sending unit may be going bad because the needle bounces slightly at about half a tank. I know I can take it somewhere and pay to have it fixed BUT I want to learn more about these systems . I've worked all my life on heavy duty/diesel equipment and am enjoying the challenge Thank you to any and all that can shed some knowledge for me OH, it's a 1998 Chevy Silverado 1500 with the 5.7 liter V8 . THANKS Again, Vern

 

p0446 is a vent solenoid dtc


the normally open vent solenoids can go bad and not close during evap leak testing.


key on, unplug the connector to the solenoid. it is located on the evap canister. one wire should have power at all times with key on. use a test light to test it, not a dvom....the test light acts as a load.


connect the connector and using a fused jumper wire; backprobe the grd wire. this will power the solenoid...you should hear an audible click as the solenoid closes. if if does not click, replace the solenoid.

 

please note correction

 

Thank you for your Tec advice !!! Before I purchase the solenoid , I just wanted clarify the "back probe " procedure . Do you mean to jumper the neutral wire straight to a different ground source by cutting in to the harness and jumping straight to the negative battery post , for example ? Thanks for your expertise !!!

 

by neutral you mean grd?

you just need to provide 12 power and grd to the solenoid to make it close.







12volts is already there with key on. you need to provide the grd on the other wire to energize the solenoid (that is what the ecm does to energize the solenoid..provides grd). if you want to cut the grd wire you can but you will have to repair it later.





another option is to: go to a sewing/quilting store and buy some T-pins. slide the t-pin into the grd wire from the backside of the connector. connect your jumper wire from the t-pin to a good grd.

 

Good afternoon !!! I did what you said and ground jumpered the solenoid and it DID make a click , so I'm guessing it must be working , which is good but I still have the code problem . Sorry !!! Do you have any other tricks to try ? I'm a bit stubborn (and cheap) so I would love to solve this myself . Thanks for your time and expertise !!!!! Vern

 

not without test equipment. the next step is to smoke test the system for leaks.

try scottykilmer.com...he has some unique ways to smoke test an evap system.