Question for A Mechanic

[Monkey Wrench]

Folks, I'm hoping there's a mechanic that can lend a hand.

I have a 1999 Chevrolet Tahoe with 76K miles on it. Within the last six months, I have had both catalytic converters replaced and a fuel pump replaced, all by the same shop.

Recently, the "Service Engine Soon" light popped on, so I stopped by an AutoZone to have them pull the code. Here's what it referred to:

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction

Truck is now in the shop and I gave the manager the print out from AutoZone in an honest effort to try and help. The manager initially dismissed it as not being from a reliable source, but did take it all the same. I mentioned that I've had both converters and a fuel pump replaced within the last six months or so and that, while not a mechanic, given the trouble code referring to an emission control problem and converters being emission control devices, I feel that the repairs should be covered under warranty.

Ever since the fuel pump was replaced (about a month ago) everytime I refuel and remove the gas cap it sounds like air wooshing out (think of the sound a beer bottle makes when you twist the cap off slowly). It acts like the fuel tank is not venting.

So, my question is, am I at least somewhat correct in assuming that this trouble code is related to either the catalytic converter or fuel pump repairs? Could a defective gas cap trigger this error code?

Thanks in advance for the assist!

 

[.21Rc10GT]

Not too sure here, but when our suburban (2003, with 85k miles) gets that light on, its either time for an oil change or the gas cap isnt all the way tight or something (usually reinstalling the gas cap and turning it a few times solves the problem).

 

[jetmechG550]

I can only offer my condolences as my mechanical expertise is in turbine engines and these little nitro thingies, wish they would put idiot lights on a Revo or Jammin!

 

[Monkey Wrench]

I can only offer my condolences as my mechanical expertise is in turbine engines and these little nitro thingies, wish they would put idiot lights on a Revo or Jammin!

Really? I thought your expertise was in beating the snot out of people?

Anyhow, what little research I've done leads to some vent line being blocked or the gas cap going bad. What's really pissing me off is that these jokers have had the truck since before 8:00 AM this morning and still have not been able to tell me what they think is causing the code. Why do these shops always say they'll call me back when they know something when they have no intention of calling me?

 

[jetmechG550]

It's not just that shop! I think not returning calls has become a major way of life for most business'. In aviation we have TCAS (Traffic Collision Avoidance System), we also think that the manufacturer has this installed in the phone system but the acronym mean (Telephone Call Avoidance System) or basically Caller ID. I feel your frustrations brother, trust me!

 

[poorwboy]

Folks, I'm hoping there's a mechanic that can lend a hand.

I have a 1999 Chevrolet Tahoe with 76K miles on it. Within the last six months, I have had both catalytic converters replaced and a fuel pump replaced, all by the same shop.

Recently, the "Service Engine Soon" light popped on, so I stopped by an AutoZone to have them pull the code. Here's what it referred to:



Truck is now in the shop and I gave the manager the print out from AutoZone in an honest effort to try and help. The manager initially dismissed it as not being from a reliable source, but did take it all the same. I mentioned that I've had both converters and a fuel pump replaced within the last six months or so and that, while not a mechanic, given the trouble code referring to an emission control problem and converters being emission control devices, I feel that the repairs should be covered under warranty.

Ever since the fuel pump was replaced (about a month ago) everytime I refuel and remove the gas cap it sounds like air wooshing out (think of the sound a beer bottle makes when you twist the cap off slowly). It acts like the fuel tank is not venting.

So, my question is, am I at least somewhat correct in assuming that this trouble code is related to either the catalytic converter or fuel pump repairs? Could a defective gas cap trigger this error code?

Thanks in advance for the assist!

Yes it could be the gas cap is defective, not very common. It could be they messed something up when they replaced the fuel pump, because they have to drop the the fuel tank to get access to the pump, and all the emission crap goes on the tank. And yes emissions should still be covered by warranty.

 

[jetmechG550]

Ya know, now that I think of it, one of my co-workers was just talking about something similar and the o-ring on the gas cap was the culprit.

 

[digger]

I feel for ya. I used to mechanic on heavy equipment. (15 yrs or so back)
The computers have left me. If you can get a code to come up, you have to have a damn translater to tell you wtf it means. My crap usually goes to the shop too.

When they first started coming out with the computers, Dad had a '83? F250. We couldn't get it to run, so we put a different carb and distributor on it. Can't do that now though. A lot more complicated.

Did a search and came up with this. http://www.fullsizechevy.com/forums/ Maybe one of them have had the same problem.

Good luck with it bro.

 

[olds97_lss]

How much fuel is in the tank? I know when I let my 98 grand marquee get below 4 gallons or so, my check engine light comes on. I don't normally let it get lower than 9 gallons, but I was running some carb cleaner through the tank and I wanted to burn as much fuel as I could before diluting it with more fuel.

 

[SMaxxin]

That happen to my friends Jeep Cherokee, it was the fuel cap. Let us know what they found.

 

[Monkey Wrench]

Well, shop said the vent purge valve was stuck closed, so they opened it. Didn't charge me anything and the light went out.

Drove it home from the shop, then drove my son to his football game. Driving back, damn light came on again!

I'm getting tired of this crap! Time to find a new shop, I think!

 

[.21Rc10GT]

Well, shop said the vent purge valve was stuck closed, so they opened it.

It was "stuck" closed... They didnt replace it? There was obviously something wrong with it...

 

[FastEddy]

Sounds to me like they removed the light bulb from behind the dash.
Fixes this issue and every other ID10T light issue forever.

 

[vbgagnon]

My check engine light came on my trailblazer a few times. Once was the air filter (dirty) the other time the gas cap wasn't on correct. The third time I went to my local quick lube place and had them check the computer (I know the manager he did it) it turned out to be the same thing your having a problem with. He just reset the computer and I haven't had a problem yet. It took about 2 minutes to check/clear and I havn't had the problem reappear and its been about 4 months.

 

[Monkey Wrench]

Digger, thanks for the link, my man! I appreciate it! Got my question posted, so we'll see if those folks are as helpful as the one's here!

Pisses me off those idiots didn't replace that valve! I'd of made them do it if I absolutely didn't need my truck today!

 

[cavicatz24]

Sorry. That code is unrelated to the catalytic converter and pump. Though a component of the emission system, it is not a component covered under the same warranty as the converters. If I remember correctly, that vent is what allows air to be pulled into the system after vacuum is drawn from the tank. If it is stuck closed, vacuum cannot be released. If it is stuck open, vacuum cannot be attained. Either way, if I'm thinking of the right component, it is simply a electric valve in or on the fuel tank. (Chevrolet may have a different design than Ford). I do not think a gas cap will trigger this code, as (at least in Fords) there is a seperate Evap test that will trigger a light if target vacuum cannot be attained, but I think the system checks for actual response from the valve to trigger a valve specific code. Otherwise you'll get a major or minor evap leak code (usually major) or a gas cap loose light. Let me check the PC/ED to see exactly what will trigger that code, as OBDII codes should have similar triggers regardless of make.
*edit*
My apologies. It would appear the DTC is not used or does not apply to any Ford vehicls of that year. Either way, I doubt the cas cap is the cause and I know the evap system is only covered by the standard 3/36 warranty. I can tell you this for sure - get another mechanic. "Unsticking" the valve is garbage - all they did was clear the code because they couldn't figure it out. Your light came back on because the problem was "rediscovered" by the PCM during the drive cycle tests - it was probably never fixed (hence "no charge" for the "service") Because I work for a dealership I can tell you this with 100% certainty - go to a dealership. They cost more for a reason - nobody knows your Chevy better than a Chevy dealer. Be advised - if you live in an emission testing area you'll fail if you have the light on or if you have any DTC's stored - including P1000, which means any codes stored were just cleared and the drive cycle tests haven't been completed. The stations can tell if codes have just been cleared.
Good Luck!