Hello,
I'm having a problem with my '01 Blazer and am wondering if anyone can help me out. If kept full the truck is fine, but any time the gas tank gets below half the SES light comes on and throws a P0440 code. If I fill it back up and erase the codes it's fine as long as it's kept above half. The only problem is it still won't pass inspection. My regular mechanic (pretty shady guy, but I won't get into that unless someone thinks it's a problem) keeps telling me to make sure the light stays off and to drive it 50 or 60 miles and bring it back. I've done this numerous times and he still just says it's throwing the same two codes, and that the only solution is to try driving it longer or replace the computer. I'm no professional so I'm a little lost as to what to do from here. The only clues I can provide is that none of this affects performance, it still runs great throughout, and that a used fuel pump was installed about 8 months ago after the original pump failed. So if anyone can help at all it will be greatly appreciated. It's getting a bit unnerving trying to dodge cops every day on my way back and forth to work. Oh, and yes I've checked the gas cap.

 

Okay.. we get the 0440. What's the other code? 0442?

And you've had this since the FP was replaced? Hmmmmmmm
- Replace the computer?!!!!! WTF! The computer doesnt measure anything other than primary voltage of charging system! it only reads external sensor outputs.

How about he just go through the {admittedly overdone} EVAP system and fix the freaking problem.

I never heard of driving distances to skate by on evap probs... only for tailpipe emissions, usually at idle. MAYBE EGR.

Dang I glad I dont live in a nanny state!

 

First - Fire your mechanic.
Second - find out what thes second code is.
Third - Come back with the info.

BTW - Dont spend any more money on the truck until you start troubleshooting the problem!

 

I agree with you

 

Well it was actually the same code twice, the second time it just appeared as something like "P0440 Pd." This hasn't happened directly since the pump was changed, this is just the first time it's needed to be inspected so this is when it becomes a problem. The mechanic is the sole reason I'm concerned. The shoddy work he's done pretty much ensures he's the only one who will pass it, and I don't want him taking advantage of that. As for the computer I've heard it resets after 50 miles of the SES light being out, allowing it to pass again.

 

Refer to my previous post.
Especially step one!

All you are to this guy is a cash cow.

Search your code in the search feature. It will tell you when the code goes away. NOT your recently fired mechanic!

 

Well the guy hasn't done anything to it, which is obviously why it still won't pass. I haven't paid him a dime aside from the inspection fee, so not exactly a "cash cow." I guess I'll just scrape up the money to get it up to par to pass elsewhere and kick this schmuck to the curb.

 

That mechanic of yours is really shady sounding, telling you to drive it and come back if the light comes back on.. hope he isn't charging you for that piece of "technical information". I agree with them, FIRE THAT BUM!!!

440 is emission related.. you said you changed the fp 8 months ago, used, was it a delco fp or was it aftermarket? A couple things that can cause a 440 code is the purge solinoid has failed, the carbon canister is clogged up and can't release the vapors, there could be a bad fuel line somewhere or a bad hose.

So the gas cap is just a PORTION of the numerous things that could of went wrong or messed up. As for a mechanic telling you "Just drive it and it'll be fine" is a crock of GARBAGE!!! You should punch him in the throat and walk away..

With a P0440 OBD-II trouble code, diagnosis can be tricky at times. Here are some things to try:

Remove and reinstall the gas cap, clear the code, and drive for a day and see if the codes come back.
Inspect the EVAP system for cuts/holes in tubes/hoses
Inspect for damaged or disconnected hoses around the Evap purge solenoid
Check and/or replace the sensor
Check and/or replace the purge valve
Have a professional use a smoke machine to detect leaks (I would NOT take it to that shady mechanic of yours either..)
Other EVAP DTCs: P0440 - P0441 - P0442 - P0443 - P0446 - P0453 - P0455 - P0456

good luck. hope it all works out.

 

Well my mechanic never just told me to "drive it and it'll be fine," he would just tell me to drive it for 50 miles with the light out and bring it back and try to pass it again. I haven't given the guy a dime to fix it, because he would half *** it and botch it anyways. And yes I know the gas cap is the simplest of the problems, I've just seen so many people jump to that first, so I mentioned it to get it out of the way. But thank you for being the first to give me useful information/troubleshooting tips. Much appreciated.

 

The reason he's saying to drive it for 50 miles and then bring it back for inspection is because under emission law you have to have so many monitors set and reading PASS in the computer for it to pass emissions inspection. Some monitors won't reset untill x number of drive cycles have completed without issue. some go by mileage, engine temp, rpm etc.

Basically he's saying he can pass you for inspection once you get x number of monitors reset without throwing a code. Otherwise the state will see that he passed it even though the computer failed it (the state monitors emissions testing equipment remotely) and his inspection liscence will get revoked.

Beyond that i can't really help you with your actual issue.