ABS Wheel sensor code

Car drives excellent, was getting ready for sale, washed it and was about to park it. It was raining, so when I backed it up it was slippery, so the traction was on, I said okay. Then all brake related lights came on. Scanned it and it said rear left sensor is wrong type. Why all of a sudden, is it the wrong type? Ot looks aftermarket but why now? Thought it was dirty, cleaned it, no change. The code is 5F20. I switched the one from other side to see, which looked more like an original OEM still no change. Put it back, and now both rears have codes, same thing, 5f1a and 5f20, tried to clear codes with no success. I monitored the speed on scanner first and rear left was only one not reading now both are not reading. Cleared codes again and now only rear left. And the code is on without even putting the car in gear, it's on while the ignition is on. I tested the 2 wires, one is ground, one has nothing which I guess is a signal wire. Not sure what to do here.