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Ask Lou P. Your Own Question
Lou P.
Lou P., ASE Certified Technician
Category: Chevy
Satisfied Customers: 3726
Experience:  building and driving chevy's since i was in the womb!!!! camaro and corvette enthusiest, access to factory diagrams and tsb's
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I have a check engine light that frequently comes on and

Customer Question

I have a check engine light that frequently comes on and goes out without service. The last time it stayed on for a period of time I had it checked out and was told it was the gas cap and I purchased another one. NOTE -- The light went out before I purchased the cap. This time its own and its smog time --Diagnosis --EVAP Circuit Malfunction-- Instruction *You need a Dealer only gas cap* I bought one and the light is still on.. How do I get it extinguished before going back to the SMOG shop?
Submitted: 1 year ago.
Category: Chevy
Expert:  Lou P. replied 1 year ago.
Hello my name is ***** ***** i will do my best to help you , i strive for EXCELLENT service and nothing more. So did you ever get the actual code that came up? It would have been a p0445 or p0440 if I'm correct. I can help but I need to know the code and a few other things.
Customer: replied 1 year ago.
Code PO446
Customer: replied 1 year ago.
I was typing the mileage and thought it was about 150 approx
Customer: replied 1 year ago.
Am I still in touch with Lou?
Expert:  Lou P. replied 1 year ago.

Yes I'm here sorry for the delay

Expert:  Lou P. replied 1 year ago.

No worries on the mileage

Expert:  Lou P. replied 1 year ago.

Give me a second to double check the code

Expert:  Lou P. replied 1 year ago.

Ok , I'm guessing it was autozone or a parts store that told you gas cap , anywho. The issue is going to be one of two valves. First most failed part is called a canister vent valve. It's located on the charcoal canister or near it which on your model should be back by the spare tire under the truck(where a spare usually is so to say ). The other part is a purge valve located on the engine on the passenger side of the intake (I will double check both positions ) , these valves are what regulate the fuel vapor flow to the engine from the gas tank. If the gas tank cannot build vacuum it throws a code for a leak which means one of two things. The vent valve is stuck open or the purge valve is stuck open

Expert:  Lou P. replied 1 year ago.

These pictures are of the purge valve and its location. The vent valve usually you can see rust on the body of the valve which indicates its failed. For the purge valve you should not be able to blow through it when removed. It should only allow air to pass when activated by the ECM. Also check your fuses labeled anything like "ECM" as they would also control the valves. Hope this information helps. Please take a second and click the box and rate my service GOOD OR EXCELLENT SERVICE if you feel I have been helpful and please request me in the future. If you feel I have not been helpful please DO NOT RATE BAD OR POOR AND WASTE YOUR MONEY , I will opt out to see if another expert can provide more or better assistance so you're not wasting your money!!. Thanks for choosing just answer. Lou. also , if you feel i deserve one , BONUSES are GREATLY APPRECIATED ! ūüėČ Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou.