The sensors are located on all 4 wheels. I couldn't find a diagram to send you. They are very expensive to replace ($40-80 a piece) not including the labor for them. It's possible that there is dust on one or more of the sensors, getting a good undercarriage and wheel wash might take care of it. To reset the computer, take off the positive and negative battery cables and touch them together, might as well clean the battery terminals while you're at it. If, after you've got a good wash and the light is still on, unless you are a very good mechanic, you'll need to take it to a good brake repair shop. I recommend replacing all the sensors at the same time so you know you've got 4 good ones. Otherwise, you could end up paying for the smae service 4 times. Hope this helps.