P0500 problems

[jamesrx300]

Hi. . My names is jamesrx300. I recently acquired a Rx300. I'm getting a P0500 code as indicated by CEL. My ABS light is also on. I verified the 2 speed sensor on top of the transmission are ok as the transmission wouldn't shift from 1st to 2nd and then from 2nd to 3rd as I disconnected each speed sensor individually as I test drove the vehicle. I suspect  the ABS might be the root cause since the ABS is illuminated. Can anyone share some information or advance troubleshooting techniques in resolving this issue.