1999 Subaru Forester. The “check engine light” came on and stayed on. Took car to dealer & was told that the problem was the knock sensor. They reset the light, it has not come back on and I have not had any repairs done. Does it hurt the car to drive it without replacing the “knock sensor”? What does the “knock sensor” do? Why hasn’t the “check engine” light come back on if there is a bad part? (Advise others that local parts stores will analyze that problem for free.)
Drive on… As long as the light stays off, there is no problem. Probably just a computer glitch or a loose connection which the dealer might have corrected without telling you…
The knock sensor detects engine detonation and retards the timing. You could have a knock sensor going bad, and it might turn on the CEL again sometime. For now, if the CEL is off, drive on and don’t worry about it. If it eventually goes completely bad, yes, it might cause engine damage (like a hole in your pistons, etc) but that is the extreme case.