I have had a CEL with P0446 code for a couple months now.
- I have reset the code
- changed the gas cap
- changed the EVAP vent valve
- Verified power to the vent valve
- verified ground wire from computer to vent valve had continuity and no shorts
- blew air through the EVAP lines from the purge valve back to the canister and from the canister to the vent valve.
The code and CEL keep coming back. I took it in to a shop to get checked out, they said it had other codes and the intake has a leak (I don't remember what codes they got, but I remember seeing a P0171 along with P0446 a couple of times). They said since the intake is leaking it won't create enough vacuum to successfully complete the EVAP test. So they would need to replace the intake gaskets.
So my question is...
1. Can an intake leak cause a P0446?
2. Is there a way to verify a leak in the intake?

 

I have an 03 also. I don't remember the codes but I had 7 come up and they all were caused by the intake gasket. I had it at several different shops and each did there own thing to remove the codes. I forget what the last shop used to check the intake gasket. I want to say they used some kind of spray. Hope this helped.

 

p0171 and p0174? good chance the intake gaskets are leaking vacuum...quick test would be to get brake cleaner or something close to it and spray around the intake gasket area with the engine idling...if you can hear/see the idle change its leaking....BUT if the gaskets are leaking vacuum bad enough to throw off the evap system the engine wouldnt be running very well if at all.

I rarely replace a vent valve without replacing the charcoal canister as well, if the cause of failure was being clogged up with dirt (which it usually is) then the canister would also be full of dirt.