Q: P0446 Check engine code

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I recently got my vehicle back from my auto shop with the check engine light on and prior bringing it there it was on. I have noticed it tells me to tigthen gas cap on my dash and the check engine light remains on. After reading the code it had multiple codes such as a P0446 code and a couple other P0 codes, one that relates to a circuit leak. Now I recently bought a new gas cap and tried replacing the gas cap but that did not work. I then recently tried replacing the EVAP vent canister and when I did I removed the old 2 port canister while the one I had purchased for my vehicle was a single port. I removed the other hose on my old canister because that one ran throught the undercarriage of my truck and was basically a air filter and the new one has a built in air filter. So I hooked the new one up and turNed my vehicle on, cleared the codes and left it running for 10 minutes. No check engine light for now, but it does still say tighten gas cap when I initially turn the vehicle on.HELP

My car has 89000 miles.
My car has an automatic transmission.

Hi there. The system will set the message if it attempts a self test and finds atmospheric pressure in the tank. The gas cap may not be the concern here as this message is directly related to a large leak in the system. This system extends from the filler neck, to the tank, to the engine, and the canister. Obviously, I would not think that a new canister is not failing, but it has happened before. A smoke test on the evaporative emission system will reveal any open leak in the system. There could also be solenoid malfunctions, loose wiring connections, or broken wires. Any of these can set codes, but the "tighten gas cap" message is simply a self check to make sure you have tightened the gas cap and not an actual diagnosis of the system. So many people have left gas caps loose and end up in the service drive over the check engine light; how would you feel if you were charged the door rate to have your gas cap tightened? I know the answer and I agree, I wouldn’t be happy about that either. I suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a check engine light inspection.

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