I ran over a small piece of lumber at night and it hit the underside a few times. After I parked and turned the engine back on, the check engine light goes on. I plug in my scanner to find it is heater downstream driver side error code. I then jack it up and look under to find everything ok but there is a small dent on drivers side downstream sensor. I buy a cheap new downstream sensor on ebay and install it, clear the error code and it works fine but in two days, the error code comes back. I have erased the error code again but after a few days, it is back. Any ideas? the wiring harness to the sensor does not appear damaged. Did I maybe buy too cheap of a sensor? It fit perfectly but was only $25. Do I have to buy AC Delco or Denso brand sensor? Maybe I will switch sensors and see if computer throws error code for passenger side.