I have 2001 Toyota Highlander. In the past year it’s been doing something incredibly annoying. When I go to fill it up with gas, something inside the tank tells the gas pump that it is full every 10 cents, so it stops fueling. It does this repeatedly…fueling,stop,fueling,stop,over and over until it reaches about 8-10 dollars, then you hear this drawn out whining noise,and it stops doing it and allows you to refuel normally until you are done. I am about to pull my hair out, filling it up with gas takes about 20 minutes now when it used to take 5. Can anyone give me any suggestions on what it might be ??
It is most likely a failed evap system component. You will most likely have to have a shop check the charcoal canister and verify it is venting properly.
If it is the charcoal canister, the problem might be from continuing to fill the tank after the first auto-shutoff. I don’t know that you do this, but it is worth mentioning to avoid the problem in the future.
^
Yup!
I repeatedly warned a friend of mine to not allow gas attendants to continually overfill the tank of his 2000 Highlander, but he ignored my advice because he wanted to sit on his butt while the fueling process took place. The result was that he wound up with the same symptoms as the OP, and the bill was in excess of $350 to replace the carbon canister.
Certain pumps seem more prone to this than others for me. Sure I should probably fix something, but filling it up on slow and pulling the nozzle out of the tank a tad works for me.
Remembering a quote from my yout, never buy a char from a mechanic!
Work around 1million 214 thousand and 7! (not just cars 
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I found that pulling the nozzle out about 1/2" can help prevent the early shut-off. I had a serious problem with that when the gas pumps here had to have vapor recovery systems. If the vapor recovery system of the gas pump was having issues, the pump would keep cutting off. That 1/2" gap seems to by-pass the system and allow the tank to vent correctly. Now, the vapor recovery systems seem to have gone away, and I haven’t had anymore issues.
OP … Inside the gasoline tank, at the bottom is the gas, above that is a mixture of air and fuel vapors. As gasoline goes into the tank during re-fueling, the air/gas fume mixture at the top of the tank must have a method to move out of the way, otherwise the air pressure in the tank will increase and the pump will shut off before the tank is full. That’s almost certainly what’s happening to you.
How this is handled varies car to car, but what is supposed to happen on many cars is that air/fuel mixture gets pushed into the charcoal canister as the tank fills, where it is absorbed by the charcoal. The canister has a vent to allow air – but not the gasoline, which gets stuck to the charcoal – out into the atmosphere, preventing the air pressure in the tank to go up. So something is wrong with that on your car for some reason. Either the charcoal canister is clogged, it’s vent is plugged up, one of the hoses involved with all this is clogged, or the purge valve has failed.
It is likely that a mechanical device has failed. There is a check ball in the fuel fill tube, a fuel tank overfill control valve in the top of the tank and a vent solenoid in the charcoal canister. If any of these gets stuck you won’t be able to fill the tank. Plugged hoses and damage from overfilling the tank are things I do not see in the shop.