Noticed the other day I could smell gas whenever I came to a stop or shut the truck off. Today the SES light came on and got a code well can't remember now something like PO440 but it came up as emission malfunction. I guess it could only be two things the canisiter or the purge solenoid. With 255K miles which one do you think it is? And is this a common problem?

 

Yes it is common. I cant remember which one was commonly bad, I think it was the vent valve near the gas tank. Some just got a whole new set up for $175 from the dealer cause it was happening alot. Might check with your dealer to see if this is a possible recall.

 

Would the vent valve come up as a different name. I seam to can't find that part?

 

Not sure if this your problem but have the code verified...


Subject: DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Service Engine Soon (SES) Lamp Illuminated (Replace Hose/Evaporative Emission (EVAP) Canister Vent Asm) #02-06-04-037A - (02/02/2005)
Models: 1999-2003 Chevrolet Silverado Models
1999-2003 GMC Sierra Models
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This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 02-06-04-037 (Section 06 -- Engine/Propulsion System).
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Condition
Some customers whose vehicles are operated in dusty type environments, such as farming or mining off-road type applications, may comment about the illumination of the instrument panel SES light, with a DTC of P0446 (Restricted/Blocked EVAP Vent Path) being set.

Cause
Dirt and dust intrusion into the EVAP canister vent hose assembly, resulting in restricted air flow, may cause this condition.

Correction
After following the Service Manual diagnostic P0446 and determining that the EVAP canister vent valve is the cause of the SES light, replace the existing EVAP canister vent hose assembly with a new assembly, P/N 15086429. This new assembly has an enhanced filtering capability and a filter element that can be easily removed and cleaned. To ensure correct installation, follow the procedure below.

Raise the vehicle. Suitably support the vehicle.
Disconnect the EVAP canister vent valve electrical connector.
Disconnect the vent valve pipe at the EVAP canister.
Remove and retain the EVAP canister vent valve bracket mounting bolt.
Disengage, from the underbody, the two vent valve pipe clips securing the pipe to the underbody.
Remove and discard the complete EVAP canister vent hose assembly.
Position and secure the new assembly to the underbody using the existing hole and mounting bolt.
Tighten
Tighten the bracket mounting bolt to 12 N·m (106 lb in).

Install the two vent valve pipe clips into the existing underbody holes.
Connect the vent valve pipe to the EVAP canister.
Connect the EVAP canister vent valve electrical connector.
Lower the vehicle.
When properly installed, the new EVAP canister vent hose assembly will be positioned outboard of the original installation location. This new location provides clearance for accessing the filter element for cleaning purposes. To access the filter element, disengage the filter cover to valve locking finger by gently lifting the finger upward while simultaneously rotating the filter body clockwise. After approximately 45 degrees of rotation, the filter can be disengaged from the valve by gently pulling outward. The filter cover can then be removed and the filter element and body can be washed with soap and water. Prior to reinstalling, ensure that the body and filter element are dry.

Parts Information
Part Number 15086429 Hose Asm-Evap Emis Cnstr Vent

 

Verify the code again for a better diagnostics. The vent solenoid is a common problem and replacing this solenoid is what most recommend. I've read, however, where people have replaced their vent solenoid and the problem doesn't go away.

When I bought my truck used, it had a bad fuel level sensor and I was getting several EVAP codes and my EVAP monitor would take forever to complete. When it did complete, it always gave me an EVAP system failure code. I replaced the sensor and the monitor ran quickly but I kept getting a P0446 code. It turned out my problem was actually an open ground circuit with the fuel tank pressure sensor. I haven't had a problem since fixing that issue. All together it only cost me ~$120 for the fuel level sensor and a little elbow grease doing the work myself.

My brother was having a similar problem as yours and it was his fuel cap. He was getting an EVAP code for a large leak. That only cost him ~$25.

If you smell gas and are getting a P044X series code, I would bet you have a large leak in the EVAP system somewhere. It could be as simple as a disconnected hose in the system or a bad fuel cap. I'd bet on the fuel cap if you are getting a large leak code.

The EVAP monitoring system relies on the following components:

EVAP Purge Valve
EVAP Cannister
EVAP Vent Valve Solenoid
Fuel Level Sensor
Fuel Tank Pressure Sensor
Fuel Cap

If anyone of these has aren't working correctly, you will get some sort of EVAP failure code. If this closed system is open somewhere (cracks or holes in lines or disconnected), you will get an EVAP failure code. Electrical issues such as shorts or opens can cause some of these components to operate incorrectly and lead to codes as well. The TSB listed by ruffneck4lyfe is for a restricted vent valve which is a common problem due to the mounting location of the valve and it gets plugged with road dust.

I would first check all the hoses in the EVAP system. Make sure they are all connected tightly to the components (EVAP cannister, purge valve, and vent solenoid). Check for cracked lines and where it passes by the exhaust system. It could come in contact with the tail pipe and burn through or become brittle and crack there. There's a diagnostics port (green cap) in the lines located on the left bank side of the engine. Make sure it's tight. Also, inspect the EVAP cannister for cracks or chaffing as well.

If this checks out okay, at least visually, I'd think about replacing the gas cap. Buy a direct OEM replacement cap if you do. I've heard of problems using a generic off the shelf cap from an autoparts store.

So, good luck and don't just throw parts at the problem. I'm lucky enought to have the tools and toys to help me do my own diagnostics. It might be worth the time and money to have an automotive technician diagnose your problem if you can't find the simple problems I've laid out yourself.

 

Awesome!! Well I already started to nose around underneath moving the lines and such and cleared the code. So far nothing and the gas smell has not come back??? I haven't even touched the gas cap yet but I'll check the seal tomorrow and even put the truck in the air to get a better look underneath. I went to the dealer today and had them print me out where the vent solenoid was and was told that is the most common problem, they even keep them in stock but for $150 including a new hose... That sucks.. I was going to remove the vent solenoid and try to blow it out.....

 

Well my P0440 came back today and was messing with the vent and that's where the gas smell was. Question is how to get to the clips above the tank to release the pipingthat goes to the vent solenoid??