Q: I replaced all pads and rotors. There is pulsating /grinding noise when I brake. Is it a reluctor ring or sensor?

Pull the fuse for the ABS system to disable it and then test drive the car (don’t forget to re-install the fuse later).

If the pulsating/grinding noise remains that means the ABS system has nothing to do with your problem. The reluctor ring is not an item that can wear out. Consequently, only visual inspection of the ring is required to determine if there is mechanical damage (such as missing teeth) or if the ring is mispositioned.

The sensors can be tested with any portable scope (no "machines" are required) and in any event, if a sensor did fail assuming your ABS light is not blown out, the warning light would have alerted you to the failure.

If the noise is from the service brakes, just because they put new rotors on doesn’t mean anything. Rotors can be warped right out of the box (i.e., defective) and even if they were brand new they can essentially be destroyed (warped) if a novice and/or untrained individual does not mount the rotor properly on the hub (using a tightening sequence and a calibrated torque wrench and then checking for run-out. If run-out exceeds .002 inches the rotor has to be re-indexed if possible or shimmed on the hub).

The mounting is critical, if the run out on the rotor exceeds the thickness of ONE human hair, your brake pedal will pulsate a lot. So depending on what the rest of the diagnostic reveals, your rotors might have to be measured to rule that in or out.

An additional issue is the calipers and the condition (freeness) of the sliding pins on the torque plate. If the calipers on your car are the original ones, and they have never been rebuilt, they should have been AUTOMATICALLY recycled (discarded) and replaced with Toyota rebuilt calipers (available at any Toyota dealer; do NOT use aftermarket in this application).

After a point (16 years is plenty of time) calipers have the potential to stick due to the dreadful operating conditions at the rotor. Imagine being cooked time after time at 500 degrees while being bathed in a corrosive salt bath. The reason calipers, even 16 year old ones, are not recommended for replacement by "shops" is simply because the shop has already padded the labor charges to make more profit, and once done, obviously the economics are such that nothing is left in the budget for you the consumer to buy what is indeed an essential part of the job, that is replace the calipers if they are 16 years old! If the shop charged a reasonable labor rate, you could afford the calipers. What do they care? They get paid regardless of whether the job is done properly or or not from a technical perspective.

At this point, you need a certified professional to get to the bottom of this. Consider having a mobile diagnostic, which in your circumstance will also represent a useful second opinion, in regard to your braking system pulsating.