Verified answer

Let me re-explain that , sort of jumbled it all to crap

P0446 can be a blockage or a leak, but I would lean more on a small leak than anything. I suggest you take it somewhere to insert smoke & trace the leak. The PCM/VCM monitors the vacuum/pressure in the Evap system & it knows it should reach a certain vacuum/pressure(Depending on which step it is on) at a certain timeframe. If it reaches that point to fast from a leak or too slow from a restriction, it will set that code. It goes by the fuel pressure sensor on top of the fuel tank that will tell it how much vacuum or pressure is inside the fuel system.

You could have a faulty fuel pressure sensor causing issues. Could be the wiring, connector or other things causing that. Here is what the Service Manual say it may be::::

Check for the following conditions:

•A loose, missing, damaged, incorrect or improperly installed fuel cap including the O-Ring on it

•Missing or damaged O-rings at EVAP canister fuel vapor and purge line fittings

•A cracked or punctured EVAP canister

•Incorrectly routed or damaged EVAP system purge and vapor lines

•A damaged or disconnected EVAP purge line, vent hose or fuel tank vapor line

•A stuck closed EVAP Vent Valve

•A restricted or stuck closed fuel tank rollover valve

•A poor connection at the VCM: Inspect the harness connectors for the following conditions:

– Backed out terminals

– Improper mating

– Broken locks

– Improperly formed or damaged terminals

– poor terminal to wire connection

•A damaged harness: Inspect the wiring harness to the EVAP vent solenoid, EVAP purge solenoid and the fuel tank pressure sensor for an intermittent, open or short circuit

•A kinked, pinched or plugged EVAP purge, or fuel tank vapor line. Verify that the lines are not restricted

To be absolutely honest, you will never find it unless you pretty much replace everything. This is where you need to take it to a repair shop that has the capabilities to insert smoke into the system & seal off the system with a Tech 2 scan tool & trace it. They can be a pain to find even with the proper tools to use. I would bet your looking for a small leak than a blockage. Very rare it to be a blockage, usually the vent valve is the culprit for any type of blockage if one does occur. The purge valve usually leaks, but since you replaced both of them, I would look at the fuel cap & look closely at the o-ring inside it. It should not have any cracks on it. Try to use a GM part on those, some of those cheapo fuel caps can cause that code to rest due to the way they build it & it doesnt pass GM minimum specs.

If you replace the cap with a GM part & it comes back on, it could be anything. It could be the fuel pressure sensor causing wrong readings, can be a leak on top of the tank as well or an o-ring on one of the hoses could be leaking

It is vitally long-established for gasoline pumps to run at low strain and cause intermitant issues, that you can cast off the mattress for convenient access to the pump, high-quality cost doesn't mean lengthy lasting, you're with a delco pump. That 12 months truck additionally had problems with the plug on the pump loosing connection and wanting substitute regularly burning the connector on the pump also requiring substitute