1999 Ford Contour O2 SENSORS

I just purchased a 1999 countour, the owner told me that it needed a o2 sensor. I hooked up the obd2, and it shows that upper and lower sensors are bad, so I change them, The lower wiring was burned, so I went to the wreacking yard and got the wiring. I intalled the new wire and the sensors then clear the computer. It was running the the light came on. Check it out with the scanner, again same codes. Upper and lower o2 sensors.