Check gas cap light, then P0455 & P0449.

[Opeth]

Very frustrated with this truck after just having a whole new head installed. First time towing my boat after the head swap, no issues power wise but after traveling 110-120 miles to my camp I had the check gas cap light come on. Never saw it before so I had to look up the light, checked the cap and restarted the truck. Automatically the CEL was on solid and drove into town to get them read and came back P0455 & P0449. Evap leak large, and EVAP Vent Valve/ control solinoid Circuit malfunction.

06 trailblazer 4.2L 75k miles. OE gas cap, I don't think the gas cap is causing both issues with a circuit malfunction.

Opinions on where to start?

 

[The_Roadie]

The vent valve is on the fuel tank, but the purge valve is on the driver's side of the engine block just under where they were working. Maybe they messed with the harness. Or the filler neck of the tank cracked as they're prone to do and it's a huge coincidence.

 

[Opeth]

Well I went ahead and bought a new GM gas cap and the vent solinoid hoping that's the culprit. Disconnected the battery and will see if the CEL returns.

 

[n0kfb]

Playing the ol' 'throw parts at the problem and see if it fixes it' game?

At least the gas cap is inexpensive. Were you able to find an OEM cap with a tether? I was not, and that caused me to dig a little deeper into the problem.

Let us know how it goes!

-- Dan Meyer

 

[Opeth]

Well... Dealer charged me $25 for the AC Delco OE cap with the tether, and tried $60 for the vent solinoid, I got them down to $49 just by asking them to do better since online was $45 and Advance Auto was the same if I waited 2 days.

Swapped them both Tuesday morning, disconnected the battery to reset the CEL and have drove 50-75 miles so far doing running around, not all straight shot miles. Vehicle has been started/ stopped 10-12 times with the light staying off..... : knock on wood:

I also poked around the purge solinoid location and saw what a poor job the dealership did at putting everything back together. They did not put the wire harnesses back into their retainers, broke the fuel rail clip where it attaches to the metal PCM retainer bracket, did not bolt the lower portion of the PCM bracket back to the intake manifold ( had to take macro pics with my phone to see if there were threads into the block) didn't see any luckily. Traced the hard line from the purge solinoid to the TB, didn't see any cracks. My fuel fill neck also may be on its last leg in another winter or so, the salt is taking its toll on it but didn't see anything too bad or wet spots.

 

[LikeEnvoy]

Well... Dealer charged me $25 for the AC Delco OE cap with the tether, and tried $60 for the vent solinoid, I got them down to $49 just by asking them to do better since online was $45 and Advance Auto was the same if I waited 2 days.

Swapped them both Tuesday morning, disconnected the battery to reset the CEL and have drove 50-75 miles so far doing running around, not all straight shot miles. Vehicle has been started/ stopped 10-12 times with the light staying off..... : knock on wood:

I also poked around the purge solinoid location and saw what a poor job the dealership did at putting everything back together. They did not put the wire harnesses back into their retainers, broke the fuel rail clip where it attaches to the metal PCM retainer bracket, did not bolt the lower portion of the PCM bracket back to the intake manifold ( had to take macro pics with my phone to see if there were threads into the block) didn't see any luckily. Traced the hard line from the purge solinoid to the TB, didn't see any cracks. My fuel fill neck also may be on its last leg in another winter or so, the salt is taking its toll on it but didn't see anything too bad or wet spots.

I'm about to replace my cap due to P0455. Where does the tether attach on the car? My 07 Envoy had a split end on the tether when I bought it so I have never known where it attached.

 

[Mooseman]

On the gas door, there is a hook, just to the right of that, there is a hole. That's where it goes.

BTW, a lot of people don't know, the hook is for hooking the tether onto so the dangling cap doesn't damage the paint.

 

[LikeEnvoy]

Thanks Mooseman,
So I have tried the gas cap for a few weeks and the CEL is still on. Drat.
Weather is now not freezing my ***** off so I just lowered the spare wheel and examined the plastic pipes to the canister. Can't see any cracks or broken things.
The fuel filler pipe is firmly attached to the top and to the tank.
Took the rear solenoid off the fuel tank bracket, where one of those evap canister pipes connects, and cleaned it up; tested with 12v. It pops nicely and I can blow through in one state but not the other, so likely ok.

Then took the front solenoid off - quite tricky, eh? - I could only get one hand in there most of the time. I cleaned that up too and tried blowing/sucking. Couldn't really blow through it but when sucking at either end there was a 'very' slight air flow (I could feel it was not fully blocked but letting some of my sucking effort drain away gradually). With 12v applied I can blow through from the grey end (front) but not from the black end (back). Does that sound normal?

 

[Mooseman]

Code says you have a large leak so that could mean a broken evap pipe somewhere either on the tank or anywhere in between it and the engine. Could also be one of those valves on the tank too. Might have to do some smoke tests to find the leak. Know anybody who vapes?

 

[AzTruckGuy]

Thanks Mooseman,
So I have tried the gas cap for a few weeks and the CEL is still on. Drat.
Weather is now not freezing my ***** off so I just lowered the spare wheel and examined the plastic pipes to the canister. Can't see any cracks or broken things.
The fuel filler pipe is firmly attached to the top and to the tank.
Took the rear solenoid off the fuel tank bracket, where one of those evap canister pipes connects, and cleaned it up; tested with 12v. It pops nicely and I can blow through in one state but not the other, so likely ok.

Then took the front solenoid off - quite tricky, eh? - I could only get one hand in there most of the time. I cleaned that up too and tried blowing/sucking. Couldn't really blow through it but when sucking at either end there was a 'very' slight air flow (I could feel it was not fully blocked but letting some of my sucking effort drain away gradually). With 12v applied I can blow through from the grey end (front) but not from the black end (back). Does that sound normal?

So does the front solenoid give off a P0440 EVAP SYSTEM NO FLOW DURING PURGE if its bad? I had stalling issues on my 2003 TB and I played the lets starting buying parts game to see if it gets fixed. I also have a filler pipe leak on my tank, dealer will be repairing for free as soon the tank comes in, I'm waiting before I start buying parts to get rid of the stall

 

[Mooseman]

I'd recommend fixing the filler pipe first, reset and see what happens. P0440 is pretty specific so I would suspect the solenoid. Not sure if it would be the front or rear one.

 

[AzTruckGuy]

I'd recommend fixing the filler pipe first, reset and see what happens. P0440 is pretty specific so I would suspect the solenoid. Not sure if it would be the front or rear one.

I agree with you after researching, I'll have to wait for the dealership to tell me when the tanks comes in to see if it fixes the issue

 

[LikeEnvoy]

Code says you have a large leak so that could mean a broken evap pipe somewhere either on the tank or anywhere in between it and the engine. Could also be one of those valves on the tank too. Might have to do some smoke tests to find the leak. Know anybody who vapes?

Well, I know some who smoke but not that kind of smoke; I know one who smokes those e- cigarette /vapour things but I doubt I could use that. I'll have to start asking around.

 

[HARDTRAILZ]

I had a guy at work with stalling issues on a 2002 Voy and he is showing a P0440 code. Did you determine if it is the front or rear solenoid?

 

[AzTruckGuy]

I had a guy at work with stalling issues on a 2002 Voy and he is showing a P0440 code. Did you determine if it is the front or rear solenoid?

Going to have to wait until the Dealer installs new gas tank before buying a solenoid

 

[HARDTRAILZ]

I already swapped the fuel pressure sensor and fixed it. Found he had done both front and rear solenoid without fix, so I tossed a spare pressure sensor on after some research and do far so good

 

[LikeEnvoy]

For my P0455 (gas cap warning followed by Check Engine Lamp), as I described above, I tried a new cap- no difference -then removed both solenoids and tried blowing and sucking through them. Front valve leaked slightly when sucking from grey end (where intake vacuum sucks) so I put a new one in and disconnected battery for a few minutes- fixed it - couple of weeks later and no more CEL! I attach an exploded view of the faulty valve I cracked open.
The black rubber seal was detached from the metal disc to its left so was not centred on the hole in the grey plastic part, therefore not sealing fully.

 

[Realism]

Might have to do some smoke tests to find the leak. Know anybody who vapes?

Heh heh. Fog Machine > Vape

For anyone using this method, check the fog juice ingredients (if you dont make your own).

Mineral Oil base
prolonged use can cause a gummy build up and may damage the respiratory system if inhaled for extended periods of time (rarely found in ingredients)

Polypropylene Glycol/glycerin
works great, may see a little condensation afterwards.

LIQUID AIR - WARNING - DO NOT USE.
5:1 ratio of compressed Nitrogen to oxygen. Very combustion supportive, would not recommend use unless you're aiming to replace more than vacuum connections.

Liquid Nitrogen
Very dense fog, also expensive. May be too thick to show those minute leaks.

Compressed CO2 {aka. Dry Ice}
Alternative method that is natural and cheap if you dont have a fog machine set up. Place Dry Ice in warm to hot water and it creates a fog density in between PG and Liquid nitrogen. -- One 5 gallon bucket with lid and a hose to connect. Cut sized hole for tight fit in lid. Use SMALL chips of the dry ice at a time. A little bit goes a long ways. Toss a large chunk in there and the resulting reaction of gas expansion will be something you remember.

Just food for thought from my workshop.