Does anyone know where this sensor is located and best way to access it? Photos or diagrams would be appreciated.

 

Hello,

Here is a good post that shows how to access and replace speed sensors, Lexus RX has an identical setup to an ES. It seems like you will probably need a NO.1 sensor, the one closer to the battery, but I would still check both.

Before you will replace the sensor, check it to make sure that it is bad, the procedure should be described in the post above. Also, if it is the sensor at fault, there were two companies producing them. If I remember correctly, those were Denso and Aisin. In short, you just need to make sure that brands are the same for both sensors.

Hope this helps and best of luck!