2008 Chevrolet Silverado work truck

Truck has an engine code "P0641", I think it needs a new PCM. It brakes fine but the brake light is on. V8 259K miles (New motor has 73K miles) RKI headache rack, main toolbox and tow side boxes. Nov 2018, NEW water pump Nov 2018, NEW instrument cluster Feb 2019, NEW motor was professionally installed at 185K miles. March 2020, NEW radiator fan assembly March 2020 NEW front rotors and pads June 2022, NEW battery Dec 2022, NEW inner and outer heater hoses and pressure switch April 2023, NEW throttle body