Brakes are making loud grinding noise when slowing down to stop or on an incline

A grinding or rumbling noise can also be symptoms of a wheel bearing or constant velocity joint in a driveshaft. A worn wheel bearing can also cause a 'whistling' sound (as can a worn CV joint).

A grinding noise with brakes is either worn pads causing metal to metal contact on the brake disk/rotor, or the brake backing plate catching on a spinning rotor ... or a loose/missing anti squeal brake shim (they stop the pads from rattling and vibrating).

However, as you say a mechanic has looked at the brakes and can't find anything wrong .. I think I would begin to suspect a wheel bearing or constant velocity joint on the driveshaft (front wheel drive cars).

Take it to a car parts store like Advanced Auto to get their free trouble code reading service.

Can be a bad contact in one of the cables. A bad contact in a switch or electronic switch. a bad relay, and a dozen other causes.
Please start measuring to where the power comes and where it stops. You are close to the car, we are not. For a correct diagnose use a multimeter and look under the hood.

no year, no mileage.
bad brakes, top list.
get it serviced. now.
not checking pads (for wear) and rotors for damage, every 20k, invites this.. brakes dont last for ever on any car.... get it services, better get a 100 point inspection , if you tend not to do them at all.
its a danger to you and us, on the road.

The exploding noise need more info.

The grinding when you stop is your brakes, there should be a tab thats suposed to make a squeil sound and the brake worn out has a metal to metal scrape that you should feel isnt right get it replaced asap so its just the brakes and not the rotor or the drum.

Replace your brake pads and or rotors

first, your vehicle is under factory warranty so I wouldn't play with anything. Second make sure that the emergency brake is completly off, third some vehicle drl systems only work when the vehicle is taken out of park. I hope this helps.

it sounds like it is in the pads and rotors they might be in servicable condition but if they have ever gotten hot they can start making noises and make stopping a little bit harder.

It would be your brake pads

some of the brake material used will make that sound on toyota's and lexus.you need to try a differant type of brake pad.should help.