2002 Traiblazer 4.2 P0440

[BrownHP800]

Ok, got the P0440 code on my son's Trailblazer. No other codes. Tried the easiest, gas cap. Cleared the code. Lasted about 1 day and is back. The code isn't very specific which stinks.

Changed the vent solenoid, I happened to have one here from before. Same issue.

What is next? Purge solenoid up on the engine I guess?

 

[zaid3ssaf]

Same issue here with 02 Bravada. I never got to fixing it because we have no inspections here in iowa. lol
I've seen a method where the vent and the purge solenoids can be tested by running 12V into the pins of the valves. If you here clicking, it means that they work.

 

[BrianF]

Crawl under and have a look at the fill tube. Make sure the metal portion isn't rusted and its sealed properly to the tank.

 

[TJBaker57]

Same issue here with 02 Bravada. I never got to fixing it because we have no inspections here in iowa. lol
I've seen a method where the vent and the purge solenoids can be tested by running 12V into the pins of the valves. If you here clicking, it means that they work.

Clicking only indicates the solenoid portion is responding to the electrical signal. The associated valves can still be leaking and cause a code. Particularly if you live in a dusty area or drive on dirt roads, the vent valve can get loaded with dirt and fail to seal off when the PCM does the Evap test(s).

Here is an example of the kind of dirt I'm talking about...

 

[Mooseman]

This code is pretty broad but it doesn't say a small or large leak. The charcoal canister can also get loaded up with dust and dirt.

This could be worth a shot even though it's not for the same issue. Nothing to lose except some time. I'd also just go ahead and replace the valves. Not that expensive. Reset the codes and drive.

 

[zaid3ssaf]

The charcoal canister can also get loaded up with dust and dirt.

I wouldn't be too fond of washing the canister with water. Because unless the charcoal is dried very well, it would lose most of its efficiency. Hydrophobic solvents (like gasoline) would not be picked up by wet charcoal since water is polar. In laboratory testing, we always dried charcoal in vacuum ovens. I am not sure many cycles need to be run before enough air circulates through the canister to dry the charcoal.

 

[TJBaker57]

code is pretty broad but it doesn't say a small or large leak. The charcoal canister can also get loaded up with dust and dirt.

I've been down a lot of very dusty roads. On this trip I forgot to kill the A/C as I dragged through an exceptionally dusty rutted road. Pulled in enough dust to temporarily clog my evaporator and stop all HVAC airflow!!

 

[Mektek]

You should have had it on recirculate!

 

[gmcman]

I have recently replaced all my evap components, including the filler neck, and I'm also getting the P0440 on occasion.

I'm questioning my new GM fuel cap as it doesn't seem to tighten down very hard.

I found a broken wire to the purge valve and after repairing the wire I still have the code.

Curious to what you find, I'll do the same. In regards to the canister, that's a pretty stout piece, doubtful it would leak vacuum if not damaged but anything is possible.

 

[WarGawd]

If I recall correctly when I had this issue, the P0440 actually referred to a small evap leak. Not to try to contradict @Mooseman, but I DO recall that description from somewhere. Nevertheless, after chasing evap purge and vent valves, and several different attempts at gas caps, I determined my issue was with the filler neck rust preventing the gas cap from sealing properly.

This post may have some relevance:

Gas filler neck variants?

Hey again oh ye wise and experienced members :-) So, I'm sure it comes as no surprise to many of you that my gas filler neck has gotten pretty crusty and corroded over the years. Over time I've replaced the gas cap, the purge valve and verified that the vent valve was operating freely and made...

gmtnation.com

*Edit - OOPS, P0402 was "small" I don't recall what I learned about P0440