Let's talk knock sensors (again)....
Thread Starter
Racer
Joined: Aug 2008
Posts: 315
Likes: 0
Let's talk knock sensors (again)....
I am curious as to how our knock sensors actually work...
as in, are they "microphone" type sensors, or do they pick up on a particular vibration, etc.
The reason I am asking is b/c I have been throwing the P0332 code every so often.
I am wondering if aftermarket goodies such as solid lifters, cam, and such causing extra valve train noise will trigger them. I will admit that my motor is siginificantly louder than a stock car's valvetrain.
When the code is triggered the car DEFINITELY loses power...I dont know how much timing its pulling, but its pretty much a dog.
When I recently had the car tuned using HP Tuners, the data logging showed no signs of knock, so I'm wondering what is triggering them.
I guess its possible that they need replacing but the car only has 35k miles on it and its been quite a while since I rinsed the engine off, and even then I was careful not to spray directly around the manifold.
Anyway, sorry for the long post and thanks in advance for any help.
as in, are they "microphone" type sensors, or do they pick up on a particular vibration, etc.
The reason I am asking is b/c I have been throwing the P0332 code every so often.
I am wondering if aftermarket goodies such as solid lifters, cam, and such causing extra valve train noise will trigger them. I will admit that my motor is siginificantly louder than a stock car's valvetrain.
When the code is triggered the car DEFINITELY loses power...I dont know how much timing its pulling, but its pretty much a dog.
When I recently had the car tuned using HP Tuners, the data logging showed no signs of knock, so I'm wondering what is triggering them.
I guess its possible that they need replacing but the car only has 35k miles on it and its been quite a while since I rinsed the engine off, and even then I was careful not to spray directly around the manifold.
Anyway, sorry for the long post and thanks in advance for any help.
Team Owner
Joined: Sep 2001
Posts: 23,283
Likes: 906
From: Lake Elsinore, CA
Knock Sensor (KS) System Description
Purpose
The knock sensor (KS) system enables the powertrain control module (PCM) to control the ignition timing advance for the best possible performance while protecting the engine from potentially damaging levels of detonation. The sensors in the KS system are used by the PCM as microphones to listen for abnormal engine noise that may indicate pre-ignition/detonation.
Sensor Description
There are 2 types of KS currently being used:
Both sensors use piezo-electric crystal technology to produce and send signals to the PCM. The amplitude and frequency of this signal will vary constantly depending on the vibration level within the engine. Flat response and broadband KS signals are processed differently by the PCM. The major differences are outlined below:
KS diagnostics can be calibrated to detect faults with the KS diagnostic inside the PCM, the KS wiring, the sensor output, or constant knocking from an outside influence such as a loose or damaged component. In order to determine which cylinders are knocking, the PCM uses KS signal information when the cylinders are near top dead center (TDC) of the firing stroke.
Purpose
The knock sensor (KS) system enables the powertrain control module (PCM) to control the ignition timing advance for the best possible performance while protecting the engine from potentially damaging levels of detonation. The sensors in the KS system are used by the PCM as microphones to listen for abnormal engine noise that may indicate pre-ignition/detonation.
Sensor Description
There are 2 types of KS currently being used:
- The broadband single wire sensor
- The flat response 2-wire sensor
Both sensors use piezo-electric crystal technology to produce and send signals to the PCM. The amplitude and frequency of this signal will vary constantly depending on the vibration level within the engine. Flat response and broadband KS signals are processed differently by the PCM. The major differences are outlined below:
- All broadband sensors use a single wire circuit. Some types of controllers will output a bias voltage on the KS signal wire. The bias voltage creates a voltage drop the PCM monitors and uses to help diagnose KS faults. The KS noise signal rides along this bias voltage, and due to the constantly fluctuating frequency and amplitude of the signal, will always be outside the bias voltage parameters. Another way to use the KS signals is for the PCM to learn the average normal noise output from the KS. The PCM uses this noise channel, and KS signal that rides along the noise channel, in much the same way as the bias voltage type does. Both systems will constantly monitor the KS system for a signal that is not present or falls within the noise channel.
- The flat response KS uses a 2-wire circuit. The KS signal rides within a noise channel which is learned and output by the PCM. This noise channel is based upon the normal noise input from the KS and is known as background noise. As engine speed and load change, the noise channel upper and lower parameters will change to accommodate the KS signal, keeping the signal within the channel. If there is knock, the signal will range outside the noise channel and the PCM will reduce spark advance until the knock is reduced. These sensors are monitored in much the same way as the broadband sensors, except that an abnormal signal will stay outside of the noise channel or will not be present.
KS diagnostics can be calibrated to detect faults with the KS diagnostic inside the PCM, the KS wiring, the sensor output, or constant knocking from an outside influence such as a loose or damaged component. In order to determine which cylinders are knocking, the PCM uses KS signal information when the cylinders are near top dead center (TDC) of the firing stroke.
Le Mans Master
Joined: Nov 2005
Posts: 6,993
Likes: 25
Replaced mine @ 30K, messages went away. The wells they sit in get wet and the sensors rust and fail. Your supposed to run RTV around the grommet when you redo them, I also changed the bottom seals and pigtail connector on mine while I had it apart.
The reason they are so low in the block is so they don't get extranious noises from other sources.
The reason they are so low in the block is so they don't get extranious noises from other sources.
Melting Slicks
Joined: Aug 2000
Posts: 2,618
Likes: 5
From: Overland Park KS
Check the wiring first before you do anything. The knock sensor wiring harness is on the driver side of the back of the intake. Check the wiring because the insulation can get worn on the wires running along the back edge of the heads.
Thread Starter
Racer
Joined: Aug 2008
Posts: 315
Likes: 0
I guess even more-so if the manifold has been changed too huh (FAST 90)
Le Mans Master
Joined: Nov 2005
Posts: 6,993
Likes: 25
Usually the issue is the wells they sit in get water from cleaning or oil from the bottom plug messing them up. There is a TSB I think about sealing the well plugs with RTV dams when they are replaced. The "pigtail" connector runs out the back up the intake and connects on a stalk on the back of the drivers cylinder head. I can see them from my laptop with my scanner software but they typically don't just die, you'll get sporadic noise which will set a code(s).
Thread Starter
Racer
Joined: Aug 2008
Posts: 315
Likes: 0
Ok guys, well I replaced both knock sensors tonight and double checked the wiring.
I am STILL getting P0332!!! WTF is going on with this thing?!
Is there anything else that could be causing the code to be thrown???
I am STILL getting P0332!!! WTF is going on with this thing?!
Is there anything else that could be causing the code to be thrown???
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Melting Slicks
Joined: Aug 2000
Posts: 2,618
Likes: 5
From: Overland Park KS
I'm still going to stick with the wire problem. When you have your intake swapped out it's not all that uncommon a wire gets nicked/crushed and an intermittent touch against the block is all it takes.
Be sure to check your wiring harness at the rear of the block on the driver's side. If you have had any clutch/rear end work done it's possible they pinched the wiring harness against the firewall lowering the rear end....
I'm assuming here you have a 99 or newer? There were some design issues resolved with the 99 knock sensors/wiring harness vs. the pre-99 hardware.
Be sure to check your wiring harness at the rear of the block on the driver's side. If you have had any clutch/rear end work done it's possible they pinched the wiring harness against the firewall lowering the rear end....
I'm assuming here you have a 99 or newer? There were some design issues resolved with the 99 knock sensors/wiring harness vs. the pre-99 hardware.
Thread Starter
Racer
Joined: Aug 2008
Posts: 315
Likes: 0
Its a full bolt on car. 90/90, mild cam, dual valve springs/solid lifter, Patriot Stage II heads, LT's, X-pipe, bla bla bla
I'm still going to stick with the wire problem. When you have your intake swapped out it's not all that uncommon a wire gets nicked/crushed and an intermittent touch against the block is all it takes.
Be sure to check your wiring harness at the rear of the block on the driver's side. If you have had any clutch/rear end work done it's possible they pinched the wiring harness against the firewall lowering the rear end....
I'm assuming here you have a 99 or newer? There were some design issues resolved with the 99 knock sensors/wiring harness vs. the pre-99 hardware.
Be sure to check your wiring harness at the rear of the block on the driver's side. If you have had any clutch/rear end work done it's possible they pinched the wiring harness against the firewall lowering the rear end....
I'm assuming here you have a 99 or newer? There were some design issues resolved with the 99 knock sensors/wiring harness vs. the pre-99 hardware.
There was a wire under the manifold that was pinched, but we repaired it and checked for continuity and it was fine.
Thanks for the help guys...
This is really driving me insane!!!
Team Owner
Joined: Sep 2001
Posts: 23,283
Likes: 906
From: Lake Elsinore, CA
Review and perform the diagnostics I sent. It thoroughly tests every aspect of the system to determine if it's a bad sensor, wiring, connector or other component, whether continuous or intermittent. Incidentally, your P0332 code indicates a rear sensor problem.
Also, I think the prerequisites to run the test are interesting. One of them requires that the engine RPM is between 475-975 for 10 seconds. I know with a few h/c idle settings I've seen tuners set for higher lift cams this would be a bit low so the PCM may never see this condition.
Also, I think the prerequisites to run the test are interesting. One of them requires that the engine RPM is between 475-975 for 10 seconds. I know with a few h/c idle settings I've seen tuners set for higher lift cams this would be a bit low so the PCM may never see this condition.
