you just got the most famous code for the supra LOL
there's a short circuit in the wiring there somewhere
first thing i would do is join a wire from one knock sensor wire to the other.... go for a drive and see if the light comes on
if it doesn't then one of the knock sensors are working...
next, unplug the rear knock sensor and go for a drive, if it still doesn't come up with the check engine light then knock sensor #2 or plug is faulty
if the light does come up then #1 would be faulty... to double check, plug in #2 again and unplug #1 and take it for a drive
for the check engine light to come on you have to rev past 2500rpm
also unplug each knock sensor and visually check the wiring, is it still good or has it broken?
with age and heat they tend to deteriorate
let us know how you get on
