Knock counts constantly increasing

[Skylark]

I have an 04 5.3 in an 83 Jeep CJ5. It has the P59 PCM. I noticed that the knock counts are constantly increasing at a rate of approximately 2-3 per second at idle and I was getting P0327 and P0332 codes. I couldn't imagine that was possible so I unplugged the connector at the intake and it is still doing it. I ohms checked between the connector and the PCM and everything is correct. I've never seen a shielded knock harness before but it may be picking up something. Are there any other ideas before I split the harness open and separate the knock sensors?

[Alvin]

Knock sensors either get overly sensitive or don't pick up any noise at all as they age. This is likely just bad sensors.. Replace the harness to them while your in there.

[Skylark]

The knock count is increasing with the harness completely disconnected.

[Skylark]

Thinking about it, I can simply depin the connector at the PCM to verify that my problem is in the wiring.

[Alvin]

The knock count is increasing with the harness completely disconnected.

This is not a way of diagnosing anything.

[kingtal0n]

knock codes plus the knock counts that don't make sense with the wiring disconnected leaves only the wiring and computer. I think de-pinning the wires is an acceptable diagnostic. Could be a short (98%) or bad computer (2%)

[Skylark]

That was my thoughts as well.

[Skylark]

Depinning stopped the knock counts. I then ohms checked the knock sensor connector to all of the other pins and I didn't have a problem. When I stripped the harness I couldn't find any damage but I noticed that both knock sensor wires went around the 8ga alternator charge wire multiple times. I separated the charge wire from the harness and replaced the knock sensor wires with a twisted pair just in case. No more issues during testing so I put the harness back together.

[kingtal0n]

Ah nice find. EMI gota love it. "why does the little red light on the holley crank sensor input keep blinking" I look under the dash and hes got the crank trigger wires zip tied to the starter cable. oh lawd

[Skylark]

EMI not EMF? Unbelievable!


Oh wait that is the endless loop of questionable 80's and 90's music stuck in my head...

[kingtal0n]

electromagnetic interference? Anytime current flows through a wire it generates a magnetic field around the wire which can move electrons around in other wires, inducing current. Its how an alternator works, kind of, the rotating magnet is pushing current through windings. In this way the current flowing through wires can create currents in other wires. I take shielded cables from junkyard cars and use them on the TPS, CPS, CPS, MAP, etc... and also twist the wires where I can.

The art of tuning begins with trigger and signal quality. I wouldn't try tuning a old school megasquirt without an oscilloscope for example. The OEM ecu give a big advantage because their trigger filters and pickup quality from rotating components to sensor to wires to computer are extremely well sorted. But I always go the extra mile in performance installations to shield and isolate the position sensor wiring anyways.

I know you know I'm just being information capital