Had 2 codes.
P0446 EVAP Vent Solenoid Performance
P0442 EVAP small leak
Replaced the gas cap and P0442 went away.
Cleared P0446 and the next day my scanner shows it to be pending
a look at the live data shows 0 vent commands and evap vacuum at 16.3 constantly.
Removed the gas cap, still 16.3 vacuum and just about immediately threw a P0446 code, with another P0446 code pending.
Erased the codes and still have the same vacuum reading and 0 vent commands.
Now I am trying to research this data.
Any insight will definitely be helpful.

 

I would guess your fuel tank pressure sensor is bad

 

Thanks exninja
replaced the fuel tank sensor
command evap readings started climbing the dropped to a pretty steady 12.2 +or -
evap vp started at 0 Then climbed into the single digit and is now back to 0 + or - a tenth or 2
ran the code test an now have a p0455 large leak code pending

Round 2

 

How's the tank fill tube? - these are prone to rust. Easy to check and rule out.

 

Next stop tommss
Thanks for the input.

 

Looked over the fuel tank fill
nothing obvious some rust
started it this morning and no code.
thought it might have fixed itself lol
then I found out it won’t run the test ,34 degrees is too cold
rrrr

 

Well it has been two weeks and 580 miles and the obd still has not run the the evap monitor.
actually had the Pa emmisions test done And passed today without it running.
Still curious if it has a leak. Was told to check the purge valve as they are known problems. The test monitors the ability of the system to hold a steady vacuum pressure for a certain legnth of time. The valve stuck shut would provide no vacuum while if stuck open woul not provide a steady vacuum. Off for the safety inspection on Tuesday. Will get the evap test forced to run while I am there.

 

Well got in the SS this morning to go for the safety inspection and wouldn’t you know, the evap test ran. It left me a P0442. Not the large leak code I was expecting. I was glad I had the emission test done Sunday and it passed.
So round 3 of the evap diagnosing.
I am thinking that is has to do with the the test running. It would have sealed off the system by closing the vent valve and opening the purge.
Any thoughts will be appreciated.

 

did they test your gas cap for the emissions test?
clearly you have a leak somewhere. the best option is probably a smoke test to find it.

 

The cap is new and was tested for the im.
The freeze frame data on the scanner for when the code set was really weird.
ECM 0 volts
RPM 0
ambient temp 39 degrees
ECT 174 degrees
IAT 111 degrees
weird
time for the smoke test and vacuum check the purge and vent valves.

 

I went through all of the same b.s. on mine. I eventually smoke tested it and found that my fuel lines were rotted through, right by the drivers wheel well the have a metallic tape wrapped around the lines (protect them from the exhaust heat I'm guessing), the vapor line rotted through and was causing small and large leaks. Rockauto sells a complete pre- formed fuel line kit.