At least inspect when you hear squeal. Base further work on what you see.
Your brake system needs repair immediately. The brakes are squealing because the pads are worn out, and you are hearing the warning device or the metal to metal contact of the pad and rotor. Stop driving the car and have the brakes repaired. The ABS light may or may not go out. If it does not, there is problem with the ABS. Your standard brakes will still work.
You should not drive the car until the brakes are repaired.
You should not drive the car until the brakes are repaired.
hypothisies
hypothisies
The brake pad "squealers" are telling you to have the brakes checked.
Bad logic
theory
Typically, a knocking noise when to use your brakes in the car is caused by your brakes wearing down. This means you need to get them checked out and repaired.
A repair shop can release a car with bad brakes if they were not asked to repair the brakes or the customer refused service. It is then the responsibility of the customer to have them repaired.
You should not drive the car until the brakes are repaired.
Your brakes are telling you they need replacing soon. They have a built in "squealer" designed to make a noise when the pad wear is nearing the end.