Brake light on dash?

This is telling you there is a problem with the ABS system must likely a wheel speeds sensor here is a video that shows how to get the codes.

https://youtu.be/rTtAnsOlZU4

Please let us know what you find.

Brilliant! You are the first person to recognize the change in brightness as a clue. There's at least one and usually two other switches that also turn on the red "Brake" warning light. One is a Low Fluid switch in the brake fluid reservoir. If the fluid is low, either there's a leak or the front brake pads are worn down and ready to be replaced. Don't fill the reservoir. Add just enough clean brake fluid to turn the light off, then have the brake system inspected. Be very careful to not get any petroleum-based contaminants in the brake fluid. That will turn into a real expensive repair.

The other switch is on the combination valve. Follow the two steel brake lines from the master cylinder to that valve right below it on the frame rail. There's a single wire plugged into it. Unplug that wire. If the light goes out, unequal pressures are building up in the two hydraulic systems. That's due to a leak that we have to find.

If the brake light is on, have it scanned for abs codes and checked for a hydraulic problem

Seems a fault with the ABS system is causing this.

Check the wheel sensors.

Glad to know you have the problem fixed.

Have a nice day.