The fuel level sensor on this vehicle is in the fuel tank and part of the pump module. I suspect that since it isn't accurate, the float may be stuck or the rheostat has failed. The only way to be sure is to remove it. I attached a pic of it.
To remove it and inspect. Here are the directions for replacing it. The attached pics correlate with the directions.
2004 GMC Truck Canyon 4WD L4-2.8L VIN 8
Vehicle Powertrain Management Sensors and Switches - Powertrain Management Sensors and Switches - Computers and Control Systems Fuel Level Sensor Service and Repair Procedures
FUEL LEVEL SENSOR REPLACEMENT
1. Remove the fuel tank module.
2. Disconnect the fuel level sensor electrical connector from the module.
3. Complete the following in order to remove the fuel level sensor from the module assembly:
3.1. Disengage the locking tab from the sensor.
3.2. Slide the sensor downward from the module.
1. Complete the following in order to install the fuel level sensor to the module assembly:
1.1. Align the edges of the sensor with the slots in the module.
1.2. Slide the sensor into position, ensure the locking tab is fully engaged.
2. Connect the fuel level sensor electrical connector to the module.
3. Install the fuel tank module.
What I suggest is to check that. Let me know if you have other questions,
Images (Click to enlarge)
Tuesday, May 19th, 2020 AT 8:22 PM