Same issue giving me a low voltage in fuel sending unit code but this is actually a new code but my gauge has always been messed up... always sits 3/4 or above but the difference is my entire instrument cluster dims in and out and cannot use the trip feature to calculate the gas used so that really sucks... and my brake light doesn't always illuminate when it's engaged

 

The fuel gauge and brake light issues are two separate things, two separate circuits, totally different wiring and they don't share any systems.

Fuel gauge issue is usually the fuel float pickup on the pump, sometimes the instrument cluster itself.

Brake lights is usually the switch on the brake pedal, sometimes the wiring harness in the trunk.

 

Sorry for the poor explanation. I meant the parking brake warning light on the cluster doesn't always appear.

 

There's a switch on the parking brake, might be an issue with that switch and that's where I'd start troubleshooting.