Removing the tank from a Toto back-to-the-wall toilet. The braided water hose inside the tank has ruptured.

SOURCE: Toto Toilet - no water flow to refill tank after flush

Remove the tank lid and look at the fill valve. Is it a yellow valve?
This fill valve is common on the Toto Toilets and can easliy plug with debrie.

They can be disassmbled and cleaned. however, I usually just replace the valve with Fluid Master Fill valve.
You will also want to check the water coming into the toilet by turning off the water that supplies the toilet and disconnecting the water supply line. After removing the water supply line turn on the water at the valve to make sure that the water is flowing properly. Check the supply line also to make sure it is not plugged.
Be sure and place a small container to catch the water that will come from the valve. A towell will also help from making too much of a mess.
If the Supply line and the valve are clear the problem is in the fill valve.
The G-Max system denotes the Flushiing system which is a 3" flapper that allows the water from the tank to flow into the bowl quicker.
Good Toilets!

sanray

SOURCE: loose Toto toilet seat

Lift up plastic caps located on ends of hindge behind seat. use flat screw driver and hold the nut under the outside toilet rim with your fingers or a pair of pliers. Do not over tighten or might crack the bowl.

SOURCE: need diagram of toto toilet tank inside have

You need to replace the fill valve

SOURCE: Gmax flushing system won't stop

WATER LEVEL IS NOT PROPERLY ADJUSTED. REDUCE WATER LEVEL TO FILL LINE

SOURCE: My Toto Drake toilet makes a noise like it is gasping for air

just simply clean the auto switch,the noosle where the water comes out when the floater goes down everytime the tank is empty with water.