Check engine light comes on & gas gauge goes to empty checked gas cap ok error # po463 comes up when checking with comp tool? mechanic thinks its tank level control problem. need advice .

Now have a repair shop do the proper testing & resolve

Need system diagrams,scan tool & evap smoke machine

CEL blink means gross misfire, and cat burn up
CEL on can mean 100 + possible failures
SCAN it, first.
temp move with there is air pocket on top of engine
cold engine, fill the read full at ITS CAP, now the gauge will work.
if not low on AF then the ETC is bad or its wiring messed up
look at its wires first, are they OK?

it's and intermittent,failure
cant fix it if its not broke. (true mostly)
wait till it fails?
or take it in failing.?
or buy a scan tool and use it. (far far far cheaper that)
the stop , key on, and scan it. now. see DTCs you will.
or when it fails, key off on 3 times to see DTCs NOW, not later.
see flash codes now with CEL lamp.... all jeeps do this test.

there is no other way.
sorry,

the DTC can clear (error) is 3 trips) some faster.
even the gas cap loose can trip a DTC for EVAP , like millions see.

You wouldn't think a gas cap would be that important, but it is. When it's loose or cracked, fuel vapors leak out and can throw the whole fuel system off. This causes a reduction in gas mileage and increases emissions.
What causes it: If you get an error pointing to the gas cap it means fuel vapors are leaking out of your cap. This means the cap is either cracked or just wasn't tightened well enough.
What you should do: If your car isn't feeling jerky or strange when the check engine light comes on the first you should check is the gas cap. Pull over, retighten it, and take a look at the cap to see if it has any cracks in it. Continue driving and see if the check engine light turns off. Alternately, you can purchase a gas cap for about $3 at an auto parts store. All you need to do is take the old one off and screw on the new one. If you've already made it to the store, you might as well just replace it. While not car-threatening, it's good to take care of this right away to improve gas mileage.

It sounds like you have a bad wire or connection. Did you have the fuel pump changed? The mech may have been a little sloppy. I'd bet the problem is near the top of the gas tank where the pump is.

GMC sent me a letter saying that gas guage not working has been a problem and they will fix and pay half.
Also my mechanic says that it is common to get a check engine lite when you add gas to tank, especially when you fill it. Sometimes I will take off gas cap and let air out then replace cap and the check engine lite will go off. (usually). Nothing to worry about.

this is normal, you should not have engine running when re-fueling, fuel gauge moves very slowly if key is on while fueling, turn key off and then on and should read proper level.

fuel level sensor is part of the fule pump assembly. code is telling you sensor is malfuctioning. do gauges work? if yes i would leave problem alone till you need a fuel pump

If you are a DIY'er you can get a OBDII scan tool that connects to your laptop that can tell you the error code and allow you to reset your check engine light. This will save you $80 each time over going to a mechanic for a diagnostic. They are easy to use and will help you know what the issues are if you do have to go to a mechanic.
Check out http://www.fitityourself.netau.net/OBDII.html
Sometime the check engine light comes on if you did not fit your gas cap tight enough. You need a code reader to find out the error code to help solve your problem.
If it is something simple (like a gas cap) and you do not want to get a code reader to find out what codes (problems) your vehicle computer is saying there is. You can try disconnecting the negative battery lead for 5 minutes. This should reset your check engine light. If the light comes back on, you have a problem and can take it to a mechanic or buy yourself a code reader.

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

i know that if the gas cap is loose then the check engine light will come on. as far as the fuel gauge going up and down the "float" you have in your tank could be getting stuck. This is a pain in the rear to change because you will have to drop the fuel tank and either replace the part connected (best bet) to it or make sure the passage is clear.