I get the code PO496 on my 2006 GMC Envoy. I have replaced the gas cap and cleared the code but it comes back. Any thoughts?

Check for fuel leeks but suspect a problem with fuel pump ?

In many cases since you do not have any other codes, you may want to check your gas cap to make sure it is sealing correctly. Check it and/or replace it and clear the code. If it does come back, there are several tests to do in order to narrow down where the leak or loss of vacuum is happening. Below is a description of what the code means and what causes it to set. I hope this helps.

P0449 - Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction

P0455 - Evaporative Emission Control System Leak Detected (no purge flow or large leak)

Both are refer at EVAP system; other EVAP DTCs: P0440 - P0441 - P0442 - P0443 - P0446 - P0453 - P0455 - P0456

This indicates a fuel vapor leak or lack of purge flow in the EVAP control system. It means a large leak has been detected. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

Symptoms: You likely won't notice any drivability problems.
Causes: most likely means one or more of the following has happened:
A loose or improperly affixed gas cap
A non-conforming gas cap (i.e. not factory/original brand)
Other leak or damaged piece in EVAP system

Possible Solutions: the most common repair is to:
Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
Otherwise, replace the gas cap, and/or
Inspect the EVAP system for cuts/holes in tubes/hoses (you may hear a vacuum noise or smell fuel), repair if necessary


Hope helps.

Hello: Without being there when the smoke test was performed no one can say what the results of the smoke test were. I would go back to the dealer and speak to the service director/service manager and request a new gas cap.

2003 GMC Envoy has a problem with the gas tank. The plastic tank cracks at the filler neck inlet, causing some gas leakage and code P0440. GMC replaces gas tanks for free (up to 160?).

See or call your local auto parts store such as AutoZone or O'Reillys for the trouble code definition. Also, make sure your gas cap is really secure, and I mean tight.
Rick

This is a safety feature that the vehicle brings. You need to reset the E.C.U on dealership or it will keep doing it to you. It was probably caused by one single time that you did not closed the fuel cap correctly. Good luck

Then either it's the wrong fuel cap, or you have a leak else where. I'd look under the back at the fuel tank where the fill hose goes to the tank. The tanks like to break there. Most of the time people smell the gas before the light is set, but it may be differant in your case.

NO , gas cap not the issue here . the P2176 refers to throttle actuator control system - idle position not learned .... the test for this is a mile long , i would try clearing the code , and see if it returns , or it will reset itself if it see's 3 drive cycles without a failure . cheers.

I just had the same problem and the dealer told me that it was an erratic gas gauge. They needed to fix it.