Knock Sensor connectors

[South VA]

1996 GMC K2500 Suburban 7.4L. I recently started monitoring Knock Sensor counts via the DashCommand app on my phone. I recall looking at them before I knew what they were (there are two in the 7.4). And, like other underhood components in this particular Suburban, the wire to at least one of the sensors shows evidence of having been visited by Mr. or Ms. Packrat long ago.

I just looked again, and sure enough, not only is the wire on the driver's side chewed, the rubber boot on the sensor itself is in rough shape.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

The connector on the passenger side is held on with a zip tie, but the wire appears to be unscathed.

You must be registered for see images attach

I searched online for knock sensor connectors, and the only ones I could find have only one connector with a bare wire at the other end. To me, it looks like the connector should have a fitting on both ends, with a boot of some sort on the sensor.

You must be registered for see images attach

Does anyone here have any experience with these things? At a minimum, I want to replace the driver's side wire and connector, as I'm thinking the exposed wire could lead to a short and therefore a faulty reading on DashCommand. Any help is appreciated.

While I'm here, what time interval do the knock sensor counts represent? The normal range is 0 - 255, but is that per second, minute, or hour? I looked in the Shop Manual and couldn't locate that particular bit of information. Thanks.

 

[GoToGuy]

The sensor is the device that does the work. The connector just relays information.
I would suggest an easy method to find, or compare or just get a part number is use the " AC Delco " web site. If you enter your VIN , it will know exactly what your vehicle is. Then narrow down the category to " knock sensor pigtail " . You'll find it there, a new connector available with a length of wire installed. The connectors only fit one way. Splice in the wires matching the old one.
They are living well beyond there designed service life. That's way there getting brittle and sometimes the locking tab breaks off.
The connectors can be disassembled and individual parts replaced. But most just want it fixed.

 

[Schurkey]

You must be registered for see images attach

Looks more like a temp sensor than a knock sensor. Knock sensor is in the BLOCK, not the Cylinder Head.

Knock sensor should be farther down on the block, "next door" to the block drains. Photos of my '97 K2500 7.4L. (My block drain plugs have been replaced by draincocks.)

Right-bank knock sensor just above draincock, forward of starter motor. Covered by starter motor heat shield.

You must be registered for see images attach

Left knock sensor, forward of draincock, in oil-filter area.

You must be registered for see images attach

 

[South VA]

Looks more like a temp sensor than a knock sensor. Knock sensor is in the BLOCK, not the Cylinder Head.

Knock sensor should be farther down on the block, "next door" to the block drains. Photos of my '97 K2500 7.4L. (My block drain plugs have been replaced by draincocks.)

Right-bank knock sensor just above draincock, forward of starter motor. Covered by starter motor heat shield.

You must be registered for see images attach

Left knock sensor, forward of draincock, in oil-filter area.

You must be registered for see images attach

Ah. Got it. Thanks!

 

[scott2093]

1996 GMC K2500 Suburban 7.4L. I recently started monitoring Knock Sensor counts via the DashCommand app on my phone

If you don't have a real scanner, I'd verify the app's reliability in regards to registering knock counts by another means of testing. I'm only familiar with ALDL Droid and ALDL Scan but both of those were wonky in the ks department and I could never makes sense of where they would come up with some of the counts they'd show.

 

[South VA]

If you don't have a real scanner, I'd verify the app's reliability in regards to registering knock counts by another means of testing. I'm only familiar with ALDL Droid and ALDL Scan but both of those were wonky in the ks department and I could never makes sense of where they would come up with some of the counts they'd show.

Good point. I do have a scan tool, and will give it a try for comparison purposes.

 

[South VA]

I’m still curious about the time aspect of the KS count. Over what time interval does it measure knocks?

 

[PlayingWithTBI]

Over what time interval does it measure knocks?

Multiple times per second depending on your PCM. I have 2 different columns on mine. One is total counts since start up and one for actual Knock Retard - i.e. 2 = 2° timing retard.

 

[South VA]

Multiple times per second depending on your PCM. I have 2 different columns on mine. One is total counts since start up and one for actual Knock Retard - i.e. 2 = 2° timing retard.

Interesting. Normal value is 0 - 255, if I recall correctly.

 

[PlayingWithTBI]

Normal value is 0 - 255, if I recall correctly.

Yep, it's a Hexadecimal thing. 2 sixteen bit words - 16 X 16 is 256 but the last bit is for negative numbers so, 255 max.