Evap code p0442 cavalier 2005

HI EVERYNE.
I have had code P0442 for a few month. Took it to my mechanic and he changed the vent solenoid unit next to charcoal canister.and code was reset. After almost 24 hour engine trouble light came back . I used OBD2 TESTER and now I have P0445. Can somebody tell me why I have now P0445 not the original ( P0442).
Please can somebody throw me to a right direction. Thanks a lot

Anybody.

HI EVERYNE.
I have had code P0442 for a few month. Took it to my mechanic and he changed the vent solenoid unit next to charcoal canister.and code was reset. After almost 24 hour engine trouble light came back . I used OBD2 TESTER and now I have P0445. Can somebody tell me why I have now P0445 not the original ( P0442).
Please can somebody throw me to a right direction. Thanks a lot

Are you sure about the p0445?...was it possibly a P0455? If so, that's for a large EVAP leak. Check your fuel cap and be sure it's tight. Make sure all the lines were connected after the vent solenoid was replaced.

HI Thank you very much for the reply. Yes you are right and it was a typing error. It should have been P0445 not P0455. I did change the gas tank cap since two nights ago and so far I have been lucky . All the connection were checked again and all OK. I will monitor if this EVAP problem is resolved or not. I will post the results. thank you.

HI
Today the engine trouble light came on and found to be P0455 ( gross leak/no flow) . Could it be the problem due to fuel pressure sensor which is located in the gas tank. Any advice
Thanking you all for your time

Yes...a bad fuel tank pressure sensor, broken/cracked evap canister, leaking purge valve, leaking/damaged line can all cause this code.

HI gmtech1 what would be the best approach or starting point to fix this problem. I have heared that smoke test is good way to start. BY the way if fuel presure sensor is suspected then can you replace the sensor itself or complete fuel pump assembly needs to be purchased. Many thanks gmtech1

Yes, smoke test is very helpful in these cases, but you need a scan tool that can "seal" the system, and control and monitor other components. Also you can replaced the pressure sensor by itself, no need to replace the whole pump assembly.

HI I can not understand that the original problem being P0442 which indicates small leak but once the vent solenoid valve was changed then I have large leak (P0455) problem. Thanks

HI I can not understand that the original problem being P0442 which indicates small leak but once the vent solenoid valve was changed then I have large leak (P0455) problem. Thanks

Well, it's possible that the new vent valve/solenoid is not closing all the way. Something that could be seen with a smoke test and a scanner to control the valve.

HI
As a matter of curiosity why I have two codes of P0455 every time I use my OBD2 reader. It is INNOVA model 3100. I obseve 01/02 top right corner of the screen when DTC button is pressed then it is the same code as previous one. WHY
Thank you

I'm not familiar with that scanner, my guess is that one of the codes is stored as history and one is stored as current.

gmtech1
Thank you for the fast reply.

HI
How to change FTP sensor. Thanks a lot

HI
How to change FTP sensor. Thanks a lot

You'll need to drop the fuel tank enough to access the sensor. Unplug it and pry it out. It may break when removing, don't sweat it if it does, remove the broken piece if you can, or just push the broken piece into the tank and install the new one with the new seal (after removing the old one).

HI Smoke test done by a mechanic and there was no obvious visible leak detected however he tested newly changed vent valve and was adviced to replace it with original GM part as did not close as commanded by his OBD tester unit so I did replaced it with original part but he code P0455 came back after 48 hours. Another mechanic suggested that I should change the purge valve. Since purge valve is very easy accessible then can somebody tell me how to test it
Thanks a lot