CEL p0325

[poolshark743]

This came on yesterday evening and immediately I heard a slight buzzing noise like a piece of metal tapping. I am assuming this sensor has gone bad or a pigtail has come loose. Where might I find the knock sensor on our car? I have an AP1, MY 01.

Thanks in advance

[repiv]

The knock sensor is buried under the intake manifold and just above the thermostat. It can be a real chore to get to.
Here is a picture of it:
http://inlinethumb30.webshots.com/5149/2384003230025981935S600x600Q85.jpg (http://good-times.webshots.com/photo/2384003230025981935zvCeYD)

Here's where it sits on the engine. This shot is taken from the front of the engine towards the firewall, but the intake manifold brace and alternator has been removed.
http://inlinethumb26.webshots.com/33753/2226332380025981935S600x600Q85.jpg (http://good-times.webshots.com/photo/2226332380025981935NxsEEk)

In this thread, "desmo4" had to change his and he has some useful information about it in the last post of this thread:

http://forums.s2kca.com/showthread.php?t=27597&highlight=knock+sensor

[poolshark743]

If this went bad would it cause the engine to knock? I only have 50k on the motor

[repiv]

Indirectly, yes. When it senses knock, the ECU will dial back timing to stop it. It usually does it so quickly and so subtly that you never know your engine is knocking. Without the sensor working, the ECU won't know if the engine knocks and won't dial back timing, thus making it more noticable. With such a high compression engine, knock is quite easy to achieve. Without a working sensor, I would advise NOT driving the car at elevated rpm OR under high throttle positions (eg. WOT) until you get it repaired. It is with high loads, that knock begins. Of course, we all know that knock can destroy an engine. In this case, you may not actually be allowed to rev it too high anyway.
Have you been doing anything in that part of the engine? It's usually when one is changing the thermostat or doing a clutch job that this thing gets broken or the wiring harness comes loose.

[poolshark743]

Last thing I have done was put in a header, nothing on the same side as the sensor.

[poolshark743]

I have removed the belt and am about to remove the alternator, but it seems a little tricky.

[repiv]

Perhaps a previous owner did some work near that area. Did you read Jonathan's posts? He managed to do it without removing too much. He reached it from below.

[poolshark743]

I have had the car since 30k miles, and his post states he had to remove the alternator. You are referring to the last post in that thread correct?

[repiv]

You are referring to the last post in that thread correct?

Yes. You might ask Jonathan how tough it was. He seemed to have no problems. Myself, I would not have done it without removing the alternator and intake brace.

[poolshark743]

I have removed the 2 mounting bolts from the alternator but it seems that it wont budge, just rotate on an axis. Where is the intake brace found?

[repiv]

The alternator is a bugger to remove. Someone else recently posted that they couldn't get theirs out either. You must rotate it to a point where it can be pried out of the rotating pivot. That anchor point pinches the alternator in and it very tough to slide out. You may have to spray it with silicone to help it slide. Getting that bolt lined up later is also frustrating.
Look under the intake manifold. You'll see the brace. You have to work blind to get those bolts out.
You might want to try Jonathan's way. Jack up the car and see if you can reach it from below.

[poolshark743]

i removed the alternator finally using a prybar to slide it out. I then jacked the car up and felt for the knock sensor and it just fell in my hand. I see the pigtail side and a side that had a small probe on it and I am assuming the rest is still connected to the block, damn it. so just remove the piece left in the block and replace? darn it, thanks repiv, u r awesome as always. looks like I wont be on the drive at the end of this week.

[repiv]

Yes, use a socket like Desmo described to unscrew what's left in the engine.
This is most likely what happened to your sensor. It probably snapped in two from vibration and was likely cracked from previous work in the area. It's quite brittle and if pushed on, will weaken and crack, only to fall apart eventually.

New one on left. Broken one in 2 pieces on right:

http://inlinethumb08.webshots.com/21767/2396542690025981935S600x600Q85.jpg (http://good-times.webshots.com/photo/2396542690025981935aAUkTH)

Different angles:

http://inlinethumb18.webshots.com/44497/2355809340025981935S600x600Q85.jpg (http://good-times.webshots.com/photo/2355809340025981935qcFtaU)

[poolshark743]

alright got the knock sensor replaced, I found that it is much easier to reach the sensor from underneath, there is actually no reason to remove anything from the top. anyone need any help with this shoot me a message. I narrowed down the damage to when I had my clutch replaced my J C autoSpec. I am assuming they accidently banged the sensor while doing my clutch job. They stated they had to remove some starter bolts which is exactly in that location, no worries though, got wholesale on the part for $134, took about 10 minutes to change once I knew where I was headed. Thanks again Repiv, u r awesome as always.

[desmo4]

The alternator is a bugger to remove. Someone else recently posted that they couldn't get theirs out either. You must rotate it to a point where it can be pried out of the rotating pivot. That anchor point pinches the alternator in and it very tough to slide out. You may have to spray it with silicone to help it slide. Getting that bolt lined up later is also frustrating.
Look under the intake manifold. You'll see the brace. You have to work blind to get those bolts out.
You might want to try Jonathan's way. Jack up the car and see if you can reach it from below.

As I have done this before I put never seize on the the alternator bolts so it will be easy to get it off next time. And everything is easier with a Mugen Airbox in the car.

Jonathan