Can't test the knock sensor like that.

Find the ECU. On the back there will be a tiny philips head potentiometer and an LED. Turn the car to "ON", the LED should be ON, twist the potentiometer all the way clockwise, pause 2 seconds, twist all the way counterclockwise. Now the LED will flash some codes out as 2 digits. # of long flashes is the first digit. # of short flashes is the second digit. Look up codes on the internet. "55" means all clear. Now repeat the clockwise-pause-counterclockwise to reset the ECU.