Codes P0449 and P0446?

DAN FRANK AMARAL

MEMBER
2003 GMC YUKON
6.0L
V8
4WD
AUTOMATIC
300,000 MILES

Engine idling rough both po 449 and po 446 code are coming up on the diagnostic check and when I open the gas tank there's a lot of pressure that comes off of it. Just trying to figure out what needs to be replaced.

Thursday, November 16th, 2023 AT 6:10 PM

1 Reply

JACOBANDNICKOLAS

MECHANIC
108,254 POSTS

Hi,

Based on the codes, I suspect there is a blockage in the canister vent system. It could be related to a damaged evaporative emission (EVAP) vent housing, a temporary blockage at the EVAP vent solenoid inlet, or a pinched vent hose.

My first suspect is the canister vent valve has failed. Please keep in mind, it could also be something as simple as a fuel cap issue (based on the P0446), but the P0449 points me in the vent valve direction.

I attached a pic below and highlighted the location of the vent valve. Inspect it for a wiring or connector issue. Also, check hoses to and from it for damage. If everything appears to be good, then remove it for inspection. Check to see if there is evidence of a blockage or anything preventing airflow.

If nothing is obvious, disconnect the connector from the evap canister and see if you can blow air through the hose. If you can, replace the canister vent solenoid. I'm somewhat confident that is the problem.

Let me know.

Joe

See pics below.

Images (Click to make bigger)