P0446-What next, maybe a bad FTP sensor?

Bula · May 21, 2015

Hello all,

New guy here. Can't seem to find an answer elsewhere online then I found this forum.

Here's my deal. P0446 came on. Replaced the purge valve, the intake solenoind AND the Evap canister. At every replacement I thought I nailed it. That damned P0446 came on after each of the 3 fixes. I have a jinky Fuel Level Gauge so my next thought was to change out the whole FTP, Fuel Pump, fuel sending unit. Any thoughts?

Ive read it may be a bad FTP or seal throwing the P0446 code? Any ideas? Thanks in advace.

newdude · May 21, 2015

Possible. I'd see if the top of the sender is rotted as that can cause a vapor leak.

tbarn · May 27, 2015

Just so you understand, the purge valve is mounted to the engine. The vent valve is under the truck in the vicinity of the canister.

This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path that would cause excess amounts of vacuum to be developed in the EVAP system. With the purge valve open and the canister vent valve open, if the EVAP system vacuum goes above a calibrated threshold, the test will fail.

Bula · May 22, 2015

Do you try and follow the DTC code ?

Not sure I follow. After each of the repairs the code was cleared and then returned with the same DTC P0446. As far As I understood (am I'm no GM Tech) there were not many parts that could throw the P0446 code. I'm still only into this about $150 (so far).

Basically the problem is, the evap purge vent valve gets clogged with dirt, especially if the truck is used in dirty conditions.

I read that too. But I've actually replaced the purge valve with a new one. Didn't work for me. Code came back on within a week or so.

Thanks for the inputs so far.

Kevinreitan · June 8, 2015

The p0446 code i got last year ended up being the fuel take pressure sensor.

gmtech4 · May 22, 2015

Do you try and follow the DTC code ?

You're throwing parts at the truck dude called " repair by shotgun"

Doug_Scott · May 22, 2015

Found this post on another site, did you happen to give this a go first?

As the title says: some might have an ses p0446, evap emissions vent circuit low. If you take it to the dealer they want 300-400.00 to fix the problem. GM has a service bulletin on this condition and have the updated part for 180.00, thats suppose to eliminate this issue.
Basically the problem is, the evap purge vent valve gets clogged with dirt, especially if the truck is used in dirty conditions. Well I figured there had to be a cheaper way to cure this problem.
Here it is:
1) find the location of the vent valve; its under the truck, locate the charcoal canister on the front of the gas tank and trace the vent line to the vent valve.
2) Take the bracket loose with a 5/8 wrench.
3) Spin the valve around so the side with the hole is facing you.
4) Take an air compressor and blow the vent valve out.
5) reinstall and clear the code and it's fixed.

Now I know the updated part from gm is supposed to keep the valve from clogging ever again, but why spend the money when all you have to do is blow out the vent valve every 50k-100kmi and save your $$$!