how to repair these codes C236 and c237

Thanks you. First page of scan, C0237 rear wheel speed sigal erratic, Second page C0236 Rear whee speed signal missing, and page three P0502 vehicle speed sensor A circuit low input. Again Thany you I would like to thanky Greg's orange auto for his help in finding the problem to my requested question. After sperking with Greg on the phone my problem was solved, even througth it cost me... The PCM (Powertrain Modual) went out. I have to say I learned a lot speaking with Greg... Thank You

I scan with a hand tool got P0502. And yes the eng. shut down and now my speed meter does not work. Thanks to Greg's Orange Auto I on the road again..(pcm) powertrain train modual went bad...