About a week ago my check engine light came on. I got it scanned and it was the rear knock sensor. I've been expecting this for awhile since my truck is nearly 10 years old. Today while driving around town I noticed that the check engine light was not on anymore. It hasn't popped back up since it's gone off. I've killed and started the truck multiple times and driven at least 50 miles since it's gone off. Any suggestions? Go ahead and change the knock sensor? Wait until it comes back on and then deal with it?