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Ron Z.
Ron Z., - Chevy Tech -
Category: Chevy
Satisfied Customers: 19052
Experience:  18+yrs experience. State Inspector and Chevy Diagnostics
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Chevy Cavalier LS: 2004 Chevy Cavalier LS check engine light

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2004 Chevy Cavalier LS check engine light on.
Not the gas cap.
Could be an EVAP issue as there is a strong smell of gas.
Had light reset a couple times, but comes back on after about 45 miles.
Any idea what this is? Any diagrams of where to look for problem and how to fix?
Wanna be able to go in and know what I'm talking about and get to the problem quicker so I can have repaired and move on with my life. :)
Hello and Welcome! My name isXXXXX and I am here to try and assist you with your question.

  • -When you went to Auto Zone and had the codes scanned, what was the "p-code" they gave you?

Customer: replied 4 years ago.

Gosh, I don't remember exactly. I wanna say P0455. Or P0442, P0456.

One of those. But I think the 1st one.

Ok. All 3 are viable codes and will take us down different paths.

If you "Wanna be able to go in and know what I'm talking about and get to the problem quicker so I can have repaired and move on with my life." - then it'd REALLY help us a TON if we had the "exact" p-code. THis way we're not guessing and wasting time going down a path we really don't need to.

Any chance I can get you to take a quick run back to Auto Zone and get me a current code?

Customer: replied 4 years ago.

I agree. Ok. It will take me about 25 min. It's just down the road from me. Be right back. Thanks.

Great! I'll be here!

Customer: replied 4 years ago.

Ok. I'm back. Yes....P0455 is the code.


Ok. The P0455 is "EVAP System Large Leak Detected". It's a very "general" code. First and foremost, double check that fuel cap. I know you said you replaced it however- you will need a cap that meets OE Specs. Those "universal" or "locking" fuel caps sold at after market parts stores do not meet OE specs, and will not seal the system correctly. I just want to completely rule this out.

If you are 100% positive the cap is good, then there are a few different possibilities from here, unfortunately. This can be a faulty EVAP Purge Solenoid, Vent Solenoid, EVAP Canister or Fuel Tank Pressure Sensor. There ARE some tests that can be done to confirm where the problem lies, but it will require the use of a scan-tool (if you have a scan-tool, I can provide the flow-chart for you). However, if you are smelling fuel then I am leaning more towards this being a Faulty/Leaking Fuel Tank pressure sensor. It's mounted to the top of the Fuel Pump Assembly at the top of the Fuel Tank.
Again, I'm sorry I can't be more specific, but with such a general code, there would really need to be some testing done. But, like I say, based on the fuel vapor smell, and the knowledge that the FTP sensors on these vehicles are a common fail item- this is where I'd suggest starting. It's a good idea to inspect the vacuum lines to/from the Purge and Vent Valves for any cracks, holes or loose/missing connections as well. If the visual inspection checks ok, I'd say FTP Sensor.
Customer: replied 4 years ago.

Ok. Thank you so much, Ron. I appreciate the details and your quick responses. You're AWESOME!

Glad I could be of some help! Have a great day!

Please remember to use the Rating System and Rate My Service once you have all the information you need. If you have any other questions, please ask me – I’ll be happy to answer follow-ups! Thank you!
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