Where is the Knock Sensor located?

Both knock sensors 1 and 2 are on the side of the engine behind the air injection pump in line with the alternator. You may need to remove the air injection pump to gain access to them. If one has failed you will want to replace both, remove the old ones, then use something to clean the mounting boss areas before installing the new ones, don't use any lubes or grease on the install. The bolts are tightened to 89 inch pounds.