Throbbing/pulsating/slight shaking at red light

was the engine on or off?

 

In any case, did you check your tire pressures? You can't just assume the sensor is faulty.

You have likely found the reason the car was for sale.

Yes, a new Brake Pump/Actuator/Accumulator (all one unit) is in your future.

The correct advice is that no brake problem is safe to drive with. If you have no brake dash lights illuminated, you can continue to drive and you might find it doesn't get worse. I'd have a plan in place for what I'd do when brake warning lights light up the dash.

 

I disagree, diagnosing the problem requires more driving/monitoring and there's multiple systems in this braking system to ensure they work and its almost impossible for all the systems to fail at the same time.

Now if you take it to shop with this concern, because it's brakes-based, odds are before they even start a diagnosis they're going to sell you all new brakes and rotors to "solve" it, then they'll come up with more repairs if it doesn't. So diagnosing the problems first will likely save you lots of money.

Can you further explain the "slight, intermittent pulsating/throbbing in the brake pedal" ?

Are you decelerating when it happens? OR just sitting at the red light? At what speed does it occur? Does it happen more or less if you're turning to the left or right while it occurs? Can you learn to re-create the sensation? Are there any other strange noises? What happens when you do super hard emergency braking at speed in an empty parking lot?

 

Seem most likely that if you feel something in the brake pedal when braking while moving it would be a concern. But if you're feeling something in the brake pedal when the vehicle is not moving and your passenger is feeling something too it's probably not brake related.

You could try pumping up the brakes next time you have that experience and see if that changes it. If you're noticing any changes in the pedal beyond it getting harder to press, you might want to bleed the brake lines and see if that addresses the symptoms?

 

If you can recreate the symptom while someone else is driving then you could jump out and pop the hood as well as walk around the car to search for the source of the vibration.

 

if you read my whole reply rather than taking one statement out of context, you will see I said basically the same thing you said, but in two short sentences rather than three paragraphs. But no matter.

So, it sounds like it is more a thing outside the brake system causing the car to lurch against the brakes, and that is what you're feeling.

The lurching is a thing, and you should be able to find more on that with a search of old posts.