Knock Sensor

[tab]

My knock sensor has always given me problems. I have rewired it twice, and I am very confident that the wiring is sound. Every connection is soldered and I used a pin to the correct slot on the p13 ECU. About every week or two, I get the CEL. I reset the ECU, and I may go two days or three weeks and the CEL comes back. I've removed the Knock Sensor, cleaned the contact, and put it back. There is nothing to service on the knock sensor.

How do I test it? Is there a way to fool the computer so that I can make 100 percent sure it is not the ECU or my wiring? Any other options?

I don't mind replacing the sensor with a new one, I'm not cheap. However, I don't want to spend $140 on a sensor that I don't need.

Any and all suggestions appreciated.

Oh, one other thing. When I get the CEL, it is usually while just cruising or lightly accelerating @ ~3000 rpms. I double checked the timing myself and it's fine.

 

[RazorRamon]

Are you using a shielded wire?
I think that you can test the knock sensor by lightly tapping the engine block with a hammer or something. If the sensor is working properly there should be some voltage at the sensor. I believe AC voltage. I've heard of this before but I've never actually tested.

 

[tab]

I am using normal wire, about 12 guage I think. I will switch to shielded if need be.

I had the same thought about tapping on the block with a hammer, but I don't know where I need to tap. I was wondering if I could put a timing light on the engine and tap the block at the same time to see if it would retard itself.

I hate intermittent problems. It would be so much easier to troubleshoot if I could just change something and see the difference. But, when it takes two weeks for a code already, it's tough to tell.

 

[radnulb]

I believe you can fool the ECU into thinking there is a knock sensor present with a resistor + cap in series. I'll talk to some of the homies at PGMFI and see what the exact components you need are. This approach will effectively make the ECU think the knocks sensor is always silent, so make sure you use decent gas and don't do anything else the knock sensor is there to prevent

 

[tab]

Yeah, that would be nice as a troubleshooting feature. I always use premium fuel, but I'm afraid to remove a safety device for the engine.

 

[tab]

A couple more thoughts. How often do these sensors actually go bad? They are sealed, and shouldn't wear out very easy. Also, can you deaden the signal a little to keep the usefulness of the sensor. Or, is the lack of signal what causes the code to kick?

 

[cycloneb18c3]

why dont u just get an ecu chip with the knock sensor disabled?

 

[tab]

Auto P13=no chippage

 

[H22AdelSol]

Why dont you call up your Honda service department and ask them? Theve solved many of my problems

 

[posol]

are you running forged pistons? forged pistons rattle lound enough to set off knock sensors all the time

 

[radnulb]

Brian's 100% right! Forged pistons + knock sensor = perpetually retarded timing.

Sorry I forgot to check on the components for fooling the ECU into thinking the knock sensor is not there. I'll try to do that today.

 

[tab]

Originally posted by pissedoffsol@Apr 1 2004, 09:09 AM
are you running forged pistons? forged pistons rattle lound enough to set off knock sensors all the time

Stock JDM H22A with a couple bolt-ons.

Good info though! I didn't know that forged pistons did that. Like usual, it's been over a week with no CEL. Can I desensitize the sensor a little with a resistor or something?

 

[tab]

Originally posted by H22AdelSol@Apr 1 2004, 01:58 AM
Why dont you call up your Honda service department and ask them? Theve solved many of my problems

Do you mean Steve and Steve? I swear, my local Honda mechanics know less than I do. The parts counter guy kicks ass, and lets me flip through or borrow any manual I need. He even let me borrow the Honda diagnostic board that clips onto your harness and saves your ecu if you probe the wrong pin.

I did the complete helms breakdown(with special tool) and was unable to find the problem. I don't have a spare ECU or spare sensor to try. That is why I am asking the wonderful people here for suggestions.

How does the knock sensor work? Is it just a ground switch? I should just go buy a new fucking sensor and sell the old one if it turns out to not be the problem.

 

[Import Builders]

Ok, don't worry, don't worry, I know what to do.
Don't sweat pal

The knock sensor is useless really.

There is no rule that says you have to have it in your block. In fact, I BET this fixes your problem.

Take it, and zip tie it to the firewall, out of sight, and then GROUND it to the chassis ground. Make sure the GROUND is solid and pure. the GROUND is everything. Without a proper ground, the CEL will go off all the time.

Problem solved. Don't worry pal. Its over now.

Jeff

 

[posol]

knock sensors are useless.

 

[dohch22a4]

How do you remove the knock sensor from the block? Does it just pull off or is it threaded? And when it's not on there, you don't need to plug up the hole, right?

 

[radnulb]

its threaded. you don't need to plug the hole.

 

[tab]

Originally posted by radnulb@Apr 2 2004, 10:56 AM
its threaded. you don't need to plug the hole.

When I pulled mine out a few weeks ago(to inspect and check for damage), I noticed that the sensor end is sealed, and the threads were completely dry. There is just a threaded relief in the block.

 

[HellBentHONDA]

Originally posted by tab@Apr 1 2004, 05:06 PM

How does the knock sensor work?  Is it just a ground switch? 

it uses a piezoelectric disc that absorbs the shock waves from knocks and exerts pressure on a metal diaphragm compressing crystals inside the disc. the disc generates a voltage signal proportional to the knock from 0-1 volt.

 

[katman]

Originally posted by tab@Apr 1 2004, 01:43 AM
Auto P13=no chippage

wrong to some extent.

AUTO P13's are chippable (to 5speed spec at least). In fact, I have a few for sale.

As far as your KS goes, curious, did you wire the KS in from scratch or was it already integrated into your engine harness?

If you wired it in from scratch, I have a feeling the problem might lie within the actual plug you are using on the KS. You might be using a 2-wire round plug which is compatible with the KS -- which would have 2 internal female connectors, one of which should be making contact with the KS's male pin (the KS has 1 single male connector pin inside of it). Perhaps whichever of the 2 wires you're using on the plug isn't the one making a direct connection to the KS male pin, hence the check engine light.

The best thing to do in this scenerio, if you have enough wiring left from the 2-wire plug, is to splice/combine the 2 wires together that are on the round connector plug, then splice the KS wire into the newly combined wiring.. (if that makes sense). In essence, you're making a "Y" connection. Doing this will ensure a connection to the KS and your ecu will be able to communicate with it - check light relieved. I did this very thing with my KS plug to make sure the KS was indeed making contact and sending a signal to the ecu and it works.

I wish I had an image to better show what I'm talking about...

Personally, I wired in my KS using a regular unsheilded wire, and I don't get any check lights for the KS at all (when I'm using an actual DOHC VTEC ecu that is). I usually run a reprogrammed ecu which has the KS disabled though.