Service Engine Light

1999 GMC Sierra 1/2 Ton 4x4 5.3 V-8 113k Miles
Service Engine light has come on several times, each time I get a P4044(I think that's the number, generic emissions) Code.
Replaced the Gas Cap & Cleared the code. It came back 2 weeks later.
What should I go after next? No issues with the way the engine is running.
Thanks in Advance, -a12vman
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wrote:

Strange, I can find no reference to a P4044 even in a GM dealer referance. ----------------- TheSnoMan.com
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I am reposting this because I mistyped the Error Code from my Diagnostic Tool. The correct error code is P0440.
Service Engine light has come on several times, each time I get a P0440( generic emissions) Code.
Replaced the Gas Cap & Cleared the code. It came back 2 weeks later.
What should I go after next? No issues with the way the engine is running.
Thanks in Advance, -a12vman
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I don't know how much it will matter, but my Saab has recently experienced the same deal. The "check engine" light came on at the dealer before I bought it. The salesman said one of his guys had put gas in it and didn't tighten down the cap. There was no stored code in the ECM, so they cleared it.
He advised me on the situation and said if it came back on, to bring the car back for further diagnostic. It's there now. I'm betting an O2 sensor is on its way out but not necessarily totally "bad" yet.
I'll let you know, it may be of some use to you.
~jp
a12vman wrote:

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a12vman wrote:

P0440 is the code your thinking of. It is a problem with the EVAP system. It is set when the EVAP system fails it's test. The test runs by closing the EVAP system and then applying a vacuum to the gas tank. The computer then looks at how long it takes for it to drop. No vacuum or rapid leak down and it sets the code.
Items to check.
EVAP Solenoid valve (on intake manifold) could be shorted or open and causing it to malfunction. Piping to the vapor canister. Purge vent valve (which closes and allows a vacuum to build in the tank). Fuel tank pressure sensor.
--
Steve W.
Near Cooperstown, New York
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Thanks Steve I'll check into it!

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Had that happen on my 04 Colorado when new. Every 3 or four months the light would come on; evap code. Dealer replaced fuel cap and did a vacuum test which showed OK. The last time I took it in, a wide awake Tech looked at the cap-seat on the fillpipe and noticed a slight dent. Replaced the fillpipe and no more codes.
Check it out.
John
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