pulsating brakes when applied? to a 2002 es300???

check your brake fluid level

Could be warped discs, air in the brake line, weak return springs,

Another possibility is corrosion on one or more of the anti-lock sensors. That could cause the computer to misinterpret the sensor's input. My 96 ES300 has that problem. When slowing to about 5-4-3 mph coming to a stop, the ABS system activates. The corrosion causes the sensor to lose its signal at that low speed, and the computer thinks the wheel is not turning. No ABS light will come on. Nothing to worry about if the the pulsation does not bother you. At least you know that the ABS is working.