what throws knock sensor codes............

[BINKSLIDE]

due to the fact that i just changed my fuel pump, filter, knock sensors and knock sensor harness....... over the course of a month now, in my spare time, job went rather smoothly except for the lack of funding... i KNOW the knock sensors arent bad, so wtf... why am i still throwing code 34...??? and why does the car want to shut itself off every once in a while...... my brain hurts!

[paranoidjack]

due to the fact that i just changed my fuel pump, filter, knock sensors and knock sensor harness....... over the course of a month now, in my spare time, job went rather smoothly except for the lack of funding... i KNOW the knock sensors arent bad, so wtf... why am i still throwing code 34...??? and why does the car want to shut itself off every once in a while...... my brain hurts!

Knock sensors are delicate and their torque specs are very precise (and low). It's easy to tighten it too much and break the housing or ceramic plates inside.

I had a small coolant leak that shorted out my KS harness (newly installed with new KS's) and I also threw a code and ran like crap. Fixed the coolant leak and no more problem.

Nothing will cause the KS code except the KS system malfunctioning - that is a simple system of a wire harness, 2 KS's, and 2 grounding/mounting bolts.

[Q45tech]

The ecu measures the resistance of each KS if outside the range it throws a code.An isolated bias voltage is applied to KS and this voltage is them measured.

Also the background noise of engine running is translated into an average voltage so a lack thereof throws a code.

[BINKSLIDE]

when this happens, in any of your experience, does the car drop RPM's by itself and go into an almost immobile limp mode until re-started? cause that's what happens to mine... i have a full tank of good gas, and this only happens after WOT blasts down the street...

also, when i changed the failed fuel pump, the control unit did NOT get changed, would this cause a lesser flow of fuel, causing knock, causing knock sensors to trigger?

keep in mind both knock sensors and their harness are brand new from dealer, and i only snugg'ed em up when i installed em to be sure of no cracking.
Modified by BINKSLIDE at 11:40 AM 12/1/2009

[paranoidjack]

when this happens, in any of your experience, does the car drop RPM's by itself and go into an almost immobile limp mode until re-started? cause that's what happens to mine... i have a full tank of good gas, and this only happens after WOT blasts down the street...

Typically, I noticed after 3 -5 minutes of driving, WOT or not, the KS condition would kick in, clearly retarding the timing and removing probably 30% power. Also, it would feel as if the transmission wasn't shifting properly, almost like it was being damaged during shifting it was so rough at times. EVERY SINGLE TIME I started the car, it would drive fine for several minutes until the CPU saw the faulty KS's.

also, when i changed the failed fuel pump, the control unit did NOT get changed, would this cause a lesser flow of fuel, causing knock, causing knock sensors to trigger?

Really don't know bud - sorry. Never changed fuel pumps. Lots of guys on here have had the FPCU fail though - so DEFINITELY worth testing it by FSM procedures.

keep in mind both knock sensors and their harness are brand new from dealer, and i only snugg'ed em up when i installed em to be sure of no cracking.

I did the job three times. First time I had a leaky coolant hose. After second time for some reason I had a KS code even though all seemed fine. Third time did the trick and it was fine. The smallest mistake, not seating the clip properly could trigger the code. As I had, could be a leak in the valley shorting out the fine components.

Search NICO for the images and info on how to OHM and test KS's at terminal end of harness, and if faulty, take it all apart and test harness alone for continuity (jiggle around while doing this).

Lastly, replace KS's again. Brand new KS's can fail INSTANTLY if dropped on the floor ONCE five years ago. It happens.

[BINKSLIDE]

see like this morning, i let the car warm up, read back code 34 knock sensors.... drove it down the block, got it to shut itself off...once it finally started again ( newsflash, the starter is weak now also, awesome...) i drove it home after the idle even'd out and it read code 55 all systems okay... like how is this possible!?

[Q45tech]

The KS [like all ceramic piezo components] are temperature sensitive. The resistance and voltage ouput [from a knock or background noise] signal varies with temperature {why KS circuitry has AGC along with frequency bandpass filters}.

Amazing things you learn in BSEE even a 30 year old one.

I periodically link electronic IC specifically designed even 20 years ago to accomplish KS system.http://www.intersil.com/data/an/an9770.pdfThe above has detailed explanation of how system detects bad KS and what it does about it ................RETARD and throw a code.

Notice how the bandpass filters can be programmed from 1kHz> 4.5 kHz to match the cylinder dimensions, cr, and head volume and material [Al vs Fe] to describe what the knock will sound like.................as all knock drives the piston directly down into the crank bearing............rattle then clink.

http://focus.ti.com/apps/docs/...+auto

[paranoidjack]

Tech, is the AGC temperature compensation control? If so, HOW is this a part of the KS system? Is it a component of the KS itself?

Thinking out loud, likely it's part of the ECU?