2004 G35 Sedan. How many hours labor or minutes to replace knock sensor harness ?

 

Remove the upper/lower plenum, lower collector and fuel rail, probably 5 or so hours. Pull the fuel pump relay and crank/run the motor till it stalls to relieve pressure. There is no bleed valve factory installed.

 

How long to replace knock sensor harness only ?

 

You have to disassemble all that stuff to get to the harness, it's buried underneath the intake and fuel delivery system. It's bolted to the top of the motor, look inside that little rectangular hole at the bottom of your intake manifold and you can see it with a flashlight.

Some folks in the past have been able to use a long piece of coathanger, needle nosed pliars, magic, and trickery to replace the harness but I've never tried so who knows.