The easiest way to check a knock sensor is to knock on the engine ...
tap it with a small hammer to see if the idle speed drops.  If it
doesn't, either your knock sensor is bad or you don't have one.  I don't
know if this vehicle has one or not.

I believe Chrysler did away with the knock sensor on the 4.0 engine back
in 92 or so.  The guys that make 4.7 strokers out of them go for the
older ones mainly to get the knock sensor feature.  I could be off on
the year they dropped it, but I still don't think you have one.

That said, even 'with' the knock sensor, my owners manuals state high
octane gas may be needed if running hot, hard or fully loaded.  It also
stated if the ping does not stop with high test, to lessen the load.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's