03 sonata when car is in drive, as i hold down on the brake pedal, feel a massive vibration running down under the car, does not go away unless i release the brake pedal or put car in neutral. thanks

Your better off going by the feel of the pedal rather than measurements. Try this. With the engine off and the brake system cold remove the key from the ignition and pump the brake pedal. it should get progressively harder and your foot travels a shorter and shorter distance until its too hard to press.
Press and hold the brake pedal hard down then start the engine. You should feel the pedal soften, that's the vacuum inside the brake booster kicking in.
Release the pedal and again press it hard down, holding it there. The pedal should feel firm and not change. Release and repeat to make sure.
If the pedal has no resistance check your work as there is no pressure in the system. If the pedal is soft or spongey re-bleed the system starting with the calliper furthest away from the reservoir.

Sounds like throttle position sensor

Warped brake rotors

if you feel the pulsation in brake pedal when stopping. its a warped brake rotor thats causing it. for bad cv joint symtoms--- Unusual noises when making turns. As you are driving on the road and you make a turn at the corner, if you start hearing unusual sounds coming from under the car then this is one of the symptoms of a bad CV joint. These noises will sound like something is clicking beneath the car every time you turn the steering wheel. Evidence of a damaged boot. Steering wheel feels heavier. The steering wheel will start to feel tighter and heavier and you can hardly make simple turns to the left or right. In severe cases you might even feel heavy vibrations like you are driving down a rocky road.

Installing new brake pads on toyota camry solara 2006 front rotors and pads and rear pads. Steering wheel would shake while breaking on 50+ miles per hour speeds. All fixed now.

im asuming you are feeling the brake pedal pulseing under your foot,should'nt be to much vibration at the wheel.
most likely the brake rotors are warped they can me turned down at a shop, or sometimes almost as cheap to buy aftermarket replacements

This is not a rich mans car so its normal. Your hearing the solinod that lets you take the car out of park after the brake is depressed so the car can't be put in gear unless the brake is on. If the noise bothers you the soliniod can be found and wrapped in insulation like a rich mans car them you can ride on feeling like a rich man too. ( the Beatles sang that a long time ago) and its still true today.

the rear drum brakes work on foot and hand brake , noise under stain does it rattle could be a loose exhaust heat shield ,

the light should not come on unless there is a problem with the system. also you would notice a problem right away if the was a problem with the brakes because the pedal would be difficult to press down on and you would not feel the pulsation of the brakes under hard braking

you have got to adjust the brake light switch so it isn't pushing on the brake peddle see right now it is holding the brake down