Knock Sensor issue - Honda Prelude Forum

dr_donahue · 01-14-2006, 01:49 PM

I just got a CEL code the other day and did a scan, i looked up the code in my service manual which is a knock sensor malfunction. I dont have my manual with me right now, so i was wondering if anybody knew how to replace the knock sensor and know where it is located. The last time i checked the manual, the sensor i believe was on the left side of the block. Any help would be greatly appreciated!

bustr · 01-15-2006, 05:48 PM

the knock sensor is in the back of the motor above the oil filter

achemze · 01-16-2006, 12:32 AM

If it is a base, its a short reach to get to it. If its a SH, you have to either a) remove i/m or b) remove atts box.

Have Fun!

mstewar · 01-16-2006, 10:26 AM

yep.. big deep socket and you're all set.. I'm sure you'll have to replace it - don't bother trying to fix it if it has seperated or something..

dr_donahue · 01-16-2006, 08:44 PM

yeah its base model, i already bought the part for about $110 so when this crazy new england weather gets warm again ill be fixing it. thanx for the help guys

JayZ98 · 01-17-2006, 10:25 AM

Damn thats expensive for a knock sensor. For future, these can be had on ebay for cheap money. I personally have used a b series one and been fine, but i have heard the voltage is different between the h and b series.

Anyways, I would suggest attempting to get at it from underneeth the car. Via the same accessible area where you would reach to get your oil filter. Or you can make it complicated on yourself, take the IM off (clean it too) and do it from the top.

HuynhM08 · 07-14-2006, 05:16 PM

Sorry guys, but what's the IM. I have a 2000 SH and I had the same problem. My service engine light came on and the code read a knock sensor malfunction. I'm trying to find one for cheap, but it's kinda hard. Do you think I should go look for one in a junkyard, or save myself the time/trouble and buy one for $100+? Anyways, what I really wanted to know was how to get to the sensor and take it out without removing anything. I'm new to this kind of stuff and I don't wanna f*ck it up just yet. Thanks.

HuynhM08 · 07-14-2006, 05:21 PM

Duh, intake manifold. That was dumb. Does anyone have pictures of where it's located or can someone paint a picture in my head?

dohcpower v2.0 · 07-14-2006, 05:53 PM

its right above the oil filter and to the right a tad... it will have a green connector on it.

HuynhM08 · 07-15-2006, 01:22 AM

Thanks dochpower. Should I buy a new one or look for an old one at a junkyard. I've been reading some forums and a lot of people talk about just switching the ECU to a p28. Is that a good idea if I plan to do future mods anyways? Would it be bad to not have a knock sensor? Does the sensor just tell me if it's knocking or does it actually manage the engine to prevent it from knocking?

dohcpower v2.0 · 07-15-2006, 07:56 AM

You could try looking for a used one, but make sure they offer some sort of warranty on it, because they get pretty fragile after a few years of being on the car.

I wouldn't run the p72 due to lack of knock sensor, but thats just my opinion.

If the knock sensor detects knock, it will add fuel to the mix to prevent the knock, so it does have a purpose.

dr_donahue · 07-19-2006, 04:47 PM

hey HuynhM08, i dont know if u started the knock sensor issue, but i fixed mine and it can get frustrating real quick, especially if u simply just use a jack on ur lude. The space is very limited and not much play. BUT it can be done with time and patience. Remember the plastic is fragile on the knock sensor so don't tighten the knock sensor too much. hope that helps

HuynhM08 · 08-01-2006, 02:51 AM

Quote:

Originally Posted by dr_donahue

Remember the plastic is fragile on the knock sensor so don't tighten the knock sensor too much. hope that helps

I just bought a knock sensor from a PO member. He said it's the right one and I trust him, but I don't see the plastic piece. Is it in the middle? Here are some pics.

HuynhM08 · 08-01-2006, 02:53 AM

If it is the right one, does anyone know how much torque to put on it and if i should use anti-seize or anything? And just to be sure, I can find it under the intake manifold right next to the oil filter right?

JayZ98 · 08-01-2006, 06:59 AM

That is the actual sensor, you will need to attach the connector from your old one to it.

I dont recall what i did mine at. Hows "not too loose, but not too tight" ??

TQ measurements are in the helms. If you dont have one (get one!) someone could look it up for you.

You can use anti-seize for good measure, but i dont think it is really nesessary.

HuynhM08 · 08-01-2006, 04:55 PM

Am i just retarted or is the knock sensor fairly difficult to find? Right now I'm trying to find where it is, but I can't find it from the bottom or the top. I have the helms manual and I have an idea of where it is, but i can't find it. I also took out my oil filter so that i can have a better view, but no luck. Can anyone help me?!?!?

HuynhM08 · 08-01-2006, 05:10 PM

If i have to take off the I/M, i'm gonna be pissed. That's a lot of freggin work. No room to work from underneath either and I can't even feel around for it. I have a SH, so I guess it's harder to get to than the base model. Has anyone changed a knock sensor on a SH before and if so, what's the easiest way?

JayZ98 · 08-01-2006, 05:19 PM

You dont have to take off the IM. It should be in plain site with a wire connecting to it from the harness/firewall. It is right below the oil filter/cooler locaiton on a base, i dont rememebr where it is on a SH.

mstewar · 08-01-2006, 05:23 PM

it's right where the block meets the head, dead center, on the block.. it's very hard to see with an SH (thanks stupid ATTS).. it's just as hard to remove the IM to get to it.. find a friend with little teeny skinny arms and have them do it for you..

HuynhM08 · 08-02-2006, 05:26 PM

Okay, so I finally managed to get to the knock sensor by taking off my intake and going from the passenger side of the engine bay, but there was still too little room to work with and i could barely get my hand in there with a ratchet. after I removed the wire harness from the plastic piece from the back of the knock sensor, i took out the old sensor. I played with the plastic piece for a while and tried to see how it would fit in the knock sensor, but it seemed like it kept wanting to slip out. there were groves in the sensor for the plastic piece to go in, but what keeps it from coming out? I was tired, and I just wanted to get it done, so i put it back in with the sensor i bought from CBags4, put everything back in it's place, took a test drive, and ......... the freggin light came on once again. Checked it with my OBD2 reader, and suprise suprise.... it was my knock sensor again. Did I do anything wrong, was the sensor bad, the plastic piece was bad, or could it be there was something wrong with the wiring?