90 300se ABS sensor location?

FOR THE FRONT ONES, LOOK UNDER HOOD, LT & RT SIDE

BIG ROUND PLUG CONNECTOR 850-1100 OHM IS THE NORM I THINK.

THE REAR ONE IS UNDER REAR SEAT RT SIDE. SAME VALUE

Those are the connectors, the hall effect sensors are located in the differential housing and on each front wheel. You can get to all sensors by unplugging the computer and measuring there if you want. You should also check the castellated ring gears to see if they are plugged up and not triggering the sensors properly - although I never had that happen. Placing a DVM on the signal lines and spinning a wheel will get you a rudimentary square wave. Wiggle the lines in the wheel well when you do this, if the signal stays there look elsewhere for your problem.