Does AutoZone scroll down to see other codes, or do they just stop at one code? The knock sensor will retard the timing as a save your ass feature if the engine temperature exceeds the norm by more than 40 degrees Celsius, or if the engine rpm's exceeds 2500, or, of course, if it senses a knock. So...codes that could come along with this code would be the engine coolant temperature sensor, the engine speed sensor, or a misfire on cylinder ___ (pick a number 1-5) code. How long has it been since a tune-up? Cap, rotor, plugs? A misfire or a badly worn plug will create pre-ignition ping. Has the temp gauge been erratic? Questions...too many questions...sorry...and I hope this helped.