kaveman

i have a 97 f150 with a 4.6 in it. i removed the intake looking for a cracked lower intake manifold,(which it was) but i found both of the wires to the knock sensor were broken off about 1inch from the sensor.
my questions are
(1) why didn't the cel set any dtc's for this, the cel works, have had it set codes before
(2) with the knock sensor wiring broken like this what does the pcm do to the igntion timing, retard it or let it advance all the way.
(3) it there a way to test the knock sensor with it off of the engine

THANKS FOR ANY & ALL HELP

RahX

Knock sensor produces a/c voltage, hook up a dvom and see how much voltage it craps out if you tap the block/intake around it with a hammer/punch LIGHTLY.

kaveman

RAHK thanks for the help! i will remove it & put it a vice & ck for voltage change when hitting the vice. that should work?
on what does the pcm do if the knock sensor is out of the curcit i would like to know & why no dtc set bt cel. maybe you can help answer this for me.
THANKS FOR THE HELP
kaveman

RahX

The engine pushes timing until it sees a signal from the knock sensor which allows for the most advanced timing possible when needed. Without a knock sensor it goes on a base timing table which is safe. If the PCM sees unwanted knock it pulls timing then dumps fuel to if that doesn't work. With the knock sensor out you should be able to hook it up to a DVOM and rattatatat it on the vice a bit and see some numbers. As for it not setting a CEL, weird things happen. They might have been making just enough contact to get the signal to the PCM. Or they might have both been touching the block close enough to eachother and completing the circuit through it