Oh when my 3.8 was knocking, I sure could hear it.
Yah a light knock is hard to hear. I have not checked but will the MS light up a warning when detecting knock? I expect it would.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.