My mother has a 2002 Subaru Forester 2.5L with 166,000 miles on it. It has been regularly maintained. The check engine light came on and she took it to Autozone. The code that it read was for the knock sensor. I went out and purchased a new knock sensor and installed it. I left the battery unplugged to reset the check engine light for about an hour. I hooked the battery up, started the car. It ran normally with no light, then after about 10 seconds, the check engine light came back on. I reset it again with the same results. She then took the car back to Autozone and they put it on the scanner and it said again about the knock sensor. So i pulled it out and cleaned the part of the motor where it was mounted to make sure it had a good ground. Re-installed and reset the light. Started it up, again ran 10 seconds normally then the light came back on. As far as I know there is only 1 knock sensor on this car, does anyone have any suggestions, I am going crazy?