Fuel gauge show incorrect readings?

Hello,

On the fuel pump module there is a float that is attached to the side of it. With the level of fuel it goes up and down. This changes resistance on the contact and that translates to the fuel level gauge.
Overtime the contact can wear off or have faulty resistance value. When that happens it will give you incorrect fuel level reading.

In order to change the fuel level sensing unit you will have to replace the fuel pump module as it is a part of that assembly.

Here are couple of helpful articles:

https://www.2carpros.com/articles/how-a-fuel-pump-works
https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

I have attached diagrams for your reference.

Please let me know of any questions.
Thank you.