I replaced the knock sensor on my 91 Legacy. I disconnected the battery for an hour to clear the codes and drove the car for 30 minutes after installing the sensor. I still have a code 22. Is this because the engine hasn't had a pinging problem yet to send a signal to the pcm? Thanks, Keith

Did you check the knock coil resistance? It might be a bad coil. The engine does not need to ping for the ecu to see the sensor. Wiring?

When you replace the knock sensor did you clean the block where it seats . It needs a good contact to the block ,also it should be torqued to 18 lbs/ft

 

SEA#3

Try clearing the codes using the connector method outlined on my site. Sometimes the battery method doesn't work.