frustrating P0446 code

[Old Bay]

2006 5.3L automatic 4x4 crew cab 1500

 

P0446

I'm due for emissions in my state in late June.

So far I have:

Cleaned the evap breather filter 
Replaced the evap canister solenoid 
Ran it for several days same code popped back up

Next round:

New gas cap (old one's o-ring was all cracked up
New evap purge valve on engine.

So as far as I know what is left of the EVAP system is the charcoal canister, the pressure sensor on top of the gas tank and possibly a cracked evap line?

Is there something I'm missing or over looking?

Also if the charcoal canister is the most likely culprit it seems rock auto has one for $63 while the local parts store is almost $200.  Is there really any difference in them?

[davester]

charm.li (website) has the vehicle-specific diagnostic procedure for that code, you can use to find what the cause of it is.

[richard wysong]

If you Google the code there are a few Utube vids on diagnosing the code

[Old Bay]

So a follow up and my fix.

I found in online searches the live data to look at on a scan tool to verify the fuel tank pressure sensor was working.  It showed an spec number towards the lower end of the rang, but in spec.  Then while it was running opened the gas cap and the pressure should change.  It didn't change even a tiny bit.  The data for the purge valve said it was open...never changed.

So then I measured the voltages on the plug for the fuel pressure sensor and they matched what it should be.  So local car quest parts had the sensor in stock...it was a bit of a pain to remove and an even bigger one to get it to actually go back in.  It helped to unbolt the driveshaft and bungie cord away from the gas tank to give a bit more room to work.

So fuel tank pressure sensor in I cleared the code, and started it up.  I went to the scan tool's live data and... Eureka! The pressure number was different and fluctuated a bit.  So took it on a short drive and pressure number varied saw the purge valve go from closed to open and back to closed.  Drove it to and from work for roughly a week plugged in the scan tool no codes.  I took it in to get tested and passed.  In my state's infinite wisdom (oops meant greed), since I pushed the test with the maximum extensions I have to take it back in by Feb '27 to 'get it back up to date', then my next test won't be until Feb '29.