In the gas tank
Generally the fuel gauge sending unit located in the fuel tank is at fault for incorrect fuel level readings.
You probably have a faulty fuel gauge sending unit.
Defective fuel sending unit.
Most likely the problem is the sending unit. A good way to verify it is to run an actuator test on the scan tool for the fuel gauge. If the gage goes through its full range then the sending unit is most likely the culprit.
bad sending unit in tank, or short in wireing.
Possible a defective sending gauge or float inside the tank.
If the fuel gauge on your 2000 Montana always reads full, it could be due to a faulty fuel level sending unit, which is responsible for sending the correct fuel level information to the gauge. Additionally, there may be an issue with the wiring or the gauge itself, causing it to malfunction. Another possibility is a short circuit, which can send a constant signal to the gauge. It's advisable to have the vehicle inspected by a mechanic to diagnose and fix the issue.
probably the sending unit. unfourtunatly the sending unit and fuel pump are made in one peice, so expect it to be expensive
Simple check is to ground the fuel sending wire at the fuel tank.If the gauge reads FULL then it is a bad fuel sending unit and you need to drop the fuel tank to replace it.If the gauge reads empty when you ground the wiring then it means you have a bad fuel gauge.I would lean strongly towards the sending unit be bad my 87 the gauge started reading about 1/4 tank less before it failed.
i have a 1990 ford ranger and my fule gauge always reads full, why?
buy a new viburam for the back of the fuel gauge on the speedo. It is a heat element that reads the sending unit in the tank
This sound like a bad temperature sending unit mainly located on the intake manifold sometimes by the thermostat housing ,it has one wire plug.