Knock Sensor DTC ???'s

[GAMEOVER]

Stock Camaro T-56 & 2004 5.7 LS1 in a 1993 RX7...
If knock sensors were not connected(Knock sensor DTC were there) during a 1/4 mile pass...What would LS1 pcm do?
Would it automatically default to low Octane table? What else? There is no power after 2500 RPM...I'm 99% positive that was culprit for low power...Just after some info...:D

[Boost]

I looked at "action taken" by the PCM for all the knock sensor related codes and did not see any indication that it would reduce power further that defaulting to the low octane table. I assume this is what you mean by "no power". There is quite a drastic difference there so I'm not suprised. Sounds like an easy fix.

[GAMEOVER]

I agree that it's pretty drastic going from a Tuned High Octane Spark table down to the Low Octane Spark table...but what I want to know is if thats all that happens when Knock sensor DTC's are present...

[Boost]

Yes, that's what I meant. No further action is taken other than a MIL.

[ippielb]

The knock sensor responds to spark knock caused by Pre-detonation of the Air/Fuel mixture. As the flame front moves out from the spark plug ignition point, pressure waves in the chamber crash into the piston or cylinder walls resulting in a sound known as a knock or ping. This is caused by using a fuel with a low octane rating, overheating, or over advanced timing. Sometimes it can be caused by hot carbon deposits on the piston or cylinder head that raise compression. A knock sensor is comprised of Piezoelectric materials; Crystals that when impacted, generate a voltage (same idea as a BBQ ignitor). This voltage is monitored by the computer, and when an irregularity is detected, the computer corrects timing in VVT (variable valve timing) engines, or triggers a DTC Diagnostic Trouble Code) in older vehicles.


Read more: http://wiki.answers.com/Q/What_does_a_knock_sensor_do#ixzz1N24uBya0

[joecar]

More info in here: http://carprogrammer.com/Z28/PCM/LS1/Holden_LS1.pdf

[joecar]

I read someplace that any knock sensor failure/DTC defaults the PCM to the LO table.

[ippielb]

I read someplace that any knock sensor failure/DTC defaults the PCM to the LO table.

This is correct, knock sensor failure puts you into the lowest octane table you have. Going from a tuned high octane table to a low table you will feel absolutely gutless.

Knock sensor replacement on LS1 engines are a pain. They're located UNDER the intake manifold. There is two sensors in two identical indentations on the top of the block. Moisture gets under the intake manifold and settles in those indentations and rusts the knock sensors. By bad design on GM's part.

To replace the senors remove your intake manifold, and pop off the two rubber grommets that are on the top of the block, there should be one wire coming out of each.
http://www.jimfancher.com/sierra/images/TifToGif.gif
There's going to be a plastic connection that connects to the top of the knock sensor. I would highly recommend purchasing two new pigtails. 90% of the time they break during removal. Easy to replace, cut the wire crimp the two wires together from the pig tail to the stock wire, heat shrink it water tight.

To remove the knock sensor just take your ratchet and socket and unscrew from the block.
http://www.jimfancher.com/sierra/images/TifToGif1.gif

Then when doing the installation, be sure to use rtv silicone to seal the grommet water tight and air tight.
http://www.jimfancher.com/sierra/images/TifToGif2.gif

[ippielb]

Here's some real pictures from an 02' 5.3l that had knock sensors replaced.

Intake Manifold Removed
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01678.jpg
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01679.jpg

One of the knock sensors
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01680.jpg
The other, you can tell why it doesn't work anymore. See the plastic from the broken connection during removal.
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01684.jpg

Both knock sensors removed
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01693.jpg

Connections on the knock sensors themselves rusted.
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01697.jpg

The block, lots of moisture in there rusted.
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01713.jpg

[ippielb]

New knock sensor wiring harness
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01723.jpg

New knock sensors installed with the harness hooked up
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01726.jpg

Silicone job on the grommet
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01732.jpg

All said and done, with a little more insurance on the top of the grommet.
http://i254.photobucket.com/albums/hh93/craigslist_album_2008/gmtruckclub/knocksensors/20090411_01755.jpg

[joecar]

Good post :cheers: they can get real yucked out...


I spray paint them with black engine paint before installing.

[ippielb]

Good post :cheers: they can get real yucked out...


I spray paint them with black engine paint before installing.

Thanks! Just thought i'd help out as much as i can, i'm more mechanical smart then tune smart.

I'm going to be installing my knock sensors next weekend, i can take more detailed pictures and instructions then if wanted. Just let me know and i'll bring the camera, i might be able to take a video as well of the whole process and time lapse it possibly.

On a side note, be sure to buy new intake manifold gaskets! Not something to cheap out on there!

[JOHNBOY]

I read someplace that any knock sensor failure/DTC defaults the PCM to the LO table.

I just logged my 04 Suburban 2500. It is throwing P0332 Knock Sensor code. It is most deffinatly using the low octane timing map. But my log shows no knock retard in 20 minutes of highway driving. I need to replace the knock sensor and harness. But I need to go to Maryland this weekend. I will just live with it till I can get it torn down.