Repeating evap problem

[Pitt84]

I have a 2006 Silverado that has thrown p0449 p0446 p0554 and now p0442 with the p0554. 

Ive recently replaced purge solinoid under valve cover the evap canister and tubing at the gas tank and rerouted it per GM’S TSB and I’ve also replaced my gas cap. I’ve had to replace several canisters over past 3-4yrs and no I don’t live in a dusty environment. But with the frequency of the codes and fixes lately which have been going on every couple weeks since mid to late February I am starting to think that I am missing some underlying problem within the evap system, so any suggestions would be appreciated. This ****** CEL is becoming a real nuisance bc I’ve tested the purge solinoid I’ve tested the canister checked all evap hoses and fittings for cracks and leaks and not coming up with anything....

[swathdiver]

11 hours ago, Pitt84 said:

I have a 2006 Silverado that has thrown p0449 p0446 p0554 and now p0442 with the p0554. 

Ive recently replaced purge solinoid under valve cover the evap canister and tubing at the gas tank and rerouted it per GM’S TSB and I’ve also replaced my gas cap. I’ve had to replace several canisters over past 3-4yrs and no I don’t live in a dusty environment. But with the frequency of the codes and fixes lately which have been going on every couple weeks since mid to late February I am starting to think that I am missing some underlying problem within the evap system, so any suggestions would be appreciated. This ****** CEL is becoming a real nuisance bc I’ve tested the purge solinoid I’ve tested the canister checked all evap hoses and fittings for cracks and leaks and not coming up with anything....

Have you done a smoke test?  Gotta do that to check the lines and fittings from front to back and especially around the fuel tank.  

[Pitt84]

Yes and nothing has detected a leak

[sefiroxx]

Or, disconnect and cap the vapor line at various points to see if problem goes away. If not then problem exists between cap and engine sensor.

 

 

[Pitt84]

Will definitely give that a shot and let ya know

[swathdiver]

When a code sets, the computer stores a freeze frame of the various sensors at the time the code set so you can compare these against the shop manual.  You need a bi-directional tool to see this like the Tech-2.

 

If a smoke test was done and there is no leak, the next likely suspect would be the ECM but the troubleshooting guide should be followed in the factory shop manual and not my guessin'!

[mjm-1957]

Get a real scan tool and see what the fuel tank pressure sensor is reading. If that sensor is skewed you can replace everything in the evap system and still have a problem. We change them all the time. Should be reading 0.0 with the engine off and key on. Next start the engine and command the vent solenoid to not venting  and the purge solenoid to about 50%  and watch what the FTP sensor does. It should slowly start showing a vacuum.If it doesnt move or is not smooth and linear  then it should be replaced. If the sensor acts normal then perform a purge and seal test. Get the vacuum in the tank to about 50% and seal the system with the scan tool,should hold vacuum for around 30 seconds with no leakage, if thats normal watch how fast the vacuum bleeds off when you open the vent solenoid, should bleed off fairly quickly to 0. Hope some of this helps.

[L86 All Terrain]

Not sure if the 800's were the same as the 900's but my 2010 had a long plastic hose that went from the evap canister by the gas tank up alongside the frame rail to the transmission, then it routed up over the trans and clipped on the passenger side of the trans. There is a sponge type filter attached to this hose by the trans. Mine was full of dirt and sand and plugged up. I changed this and my purge can and my CEL went away after clearing. Forget the fault code, this was 5 years ago now. Worth a quick look anyway, hope it helps.