For all of those of you who have wondered what is inside the mysterious knock sensor (besides a piezo electric element) here it is. This is an old one that was causing a 0303 code, though when i hooked it up to my scope i still got output from it.

The KS in question



Started dremeling it...


The connecter was holding it together so that had to go:


The plastic is very strong and resiliant. Stuff just doesnt want to break, but after a while i managed to get it to give with a screwdriver and and some needle nose pliers.

 

Finally I was able to strip the plastic all the way off. If you have any kids in the room they probably shouldnt see this.



Now I took that damn nut off the top and it started coming apart.


Here it is fully dissassembled:


From left to right, you see the metal jiggy thingy that the bolt goes through. EDIT: I got this figured out now. The bottom copper ring attatches to the bolt thingy and grounds to the engine. Then the piezo element, then a copper ring sits on top of it to carry the signal to the harness connecter, followed by a plastic bag washer, then a big *** iron ring (?), then a washer then a nut. Canadian wanted $335 for a couple piezo elements and some washers and a nut.

(Yes I know my camera sucks large, its a kodak.)

 

Are you SURE it gave you a 303 code?

 

It was a KS code anyways, i don't recall the exact number.

 

P0325 --- 0304

 

it's amazing that simple POS gives everyone so much trouble. it was that hard to get apart but just dropping one during install can break it. crazy...

 

I wonder if we can make our own, for cheap?

 

It's not extremely hard to make one, but the calibration will be impossible to get right.

Looking at the one I have here, it looks like the copper rings are just that, copper rings. In between them sits the piezo element. The whole sensor appears industructable, I see nothing at all wrong with the one I have but it was setting a code and the replacement doesn't.Maybe further dissection is in order.

 

This is an excellent, informative thread. I'm very interested in the internals of the various sensors and stuff. Thanks for the pics and description. Good work!

 

i guess if you clean the copper it will start working again,

also i dont know know how metal can listen to ping?

and what is piezo?

 

Awesome, good read. Subscribing...

 

someone could potentially make a better ks now.... just find better quality material. I found a nice place for ring Piezo's
http://www.piezo-kinetics.com/forms_and_methods.htm i think you have to do mass manufacturing with that place though, they do have a nice explanation on Piezos though

 

that little part caused so much of my blood to be spilled in the engine bay

 

The copper was clean I dont think that was the problem. The piezo is the element that creates an electrical signal when its vibrated. I cracked mine in half and its just a ferrous metal with two hair-thin metallic strips glues to the top. Its brittle as hell, and perhaps what causes this sensor to fail is that over time microscopic cracks appear in it and reduce sensitivety. But I dont have a microscope to check.

I'm glad that you guys like this write up. I'm going to dissect various parts of my car as they fail, since our cars tend to break the exact same components, and post autotopsys here. The rear O2 sensor is coming close, though i tried cleaning it and am going to see if that could fix it. But if it doesnt, well, Mr. O2 Sensor, I would like to introduce you to Mr. Dremel.

 

That was wicked.

 

i'll be here with my !

 

Quartz is a good piezo material and it is used to make your clocks, watches and computers accurate. Crystalline ceramic is used to make most piezo element due to easy shape forming. Most common application of ceramic peizo element is the beeper in your alarm watch. The copper is just electrode used to apply electric field to the piezo element in the sandwich. They can break due to overstresses such as a drop to the floor.

In a KS the function is reversed, mechanical force on the piezo element induce an electrical field on the electrode.

 

got myne on ebay for $78 with shipping.

 

Pretty cool pics, nice to see I am not the only one who likes to take things apart to see how they work. Very good job makes alot more sense when you can see something yourself.

 

nice job taking it apart, good luck taking other things apart later on in your life.

 

It looks very similar to a piezo horn tweeter element.