Thread: 0 KR rear sensor & 5-7 degrees KR front sensor

I re-wired the broken rear & seem to get readings of 0 in the rear & 5-7 in the front.

Is it possible the rear is not reading right yet not throwing a code?
Is it possible for the tune to be off only on the front banks?

If the reading is correct on both banks, I am thinking either I have a problem with one of the front cylinders, the KS is not reading right but not throwing a code or something else??
Anyone experience banks with vastly different KR readings?

Originally Posted by Elite6

I re-wired the broken rear & seem to get readings of 0 in the rear & 5-7 in the front.

Is it possible the rear is not reading right yet not throwing a code?
Is it possible for the tune to be off only on the front banks?

I assume you are talking ohms. Here was my experiance with the rear KS. http://www.grandprixforums.net/possi...ml#post1096770
If you are reading 0 ohms, then you still have a break in the wire. As you can see from my post, it was broke in two different places. The other was in front of the connector that snaps onto the PS pump. In front is from the perspective of the KS. Do you know if in the history there was a time the PS pump was pulled? If it a 3.8, it had to have been done to replace water pump, plastic elbows, or lower intake gasket.

[edit]
While I was at a local Pull-a-Part yesterday, there was an 04 GP with the front clip and hood removed. The front of the cradle was laying on the ground. I was able to snap this picture showing the connector that clips onto the PS bracket. I also grabbed the wire incase I want to go back and re-do the granddaughter's GP. Picture of the clip's position

Sorry I should have been more specific. I was talking degrees of knock - I have not tested ohms as the aeroforce gauge reads 0.0 for the rear, it used to show nothing until I fixed the wire. Front seems to be reading fine, its just really high in terms of knock.

If i were in your shoes ide say unplug front and try to simulate some knock in the rear and see if its workign correctly

Our pcm's don't read front vs rear knock. I assume you are looking KR1 and KR2.. yeah..the second one isn't used in our cars.

Well that is very strange because once I fixed the cut wire to the rear bank, I started to get a reading from KR2
That makes my KR even more puzzling now, I am having some questionable thoughts of putting on the 3.4 & seeing if the KR value changes any

Originally Posted by BillBoost37

Our pcm's don't read front vs rear knock. I assume you are looking KR1 and KR2.. yeah..the second one isn't used in our cars.

Good to know but just out of curiosity how is this shown. Do our scanners just show the highest knock read or do our scanners not read the back?

Your pcm monitors both knock sensors as noise channels, it works that into an acceptable amount of noise and uses the rest to say "here's knock sucker" and retards timing based on the knock it preceives.

We don't see a number of knock...we see degrees of timing retardation that the pcm pulls based on the noise channels.

I googled it for you.. although the FSM is much better. Here's a brief on what it basicly is/does.

PURPOSE
The knock sensor (KS) system enables the engine control module (ECM) to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The ECM uses the KS system to test for abnormal engine noise that may indicate detonation, also known as spark knock.

SENSOR DESCRIPTION
The knock sensor (KS) system uses a flat response 2-wire sensor. The sensor uses piezo-electric crystal technology that produces an AC voltage signal of varying amplitude and frequency based on the engine vibration, or noise, level. The amplitude and frequency are dependant upon the level of knock that the KS detects. The engine control module (ECM) receives the KS signal through a signal circuit. The KS ground is supplied by the ECM through a low reference circuit.

The ECM learns a minimum noise level, or background noise, at idle from the KS and uses calibrated values for the rest of the RPM range. The ECM uses the minimum noise level to calculate a noise channel. A normal KS signal will ride within the noise channel. 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. In order to determine which cylinders are knocking, the ECM only uses KS signal information when each cylinder is near top dead center (TDC) of the firing stroke. If knock is present, the signal will range outside of the noise channel.

If the ECM has determined that knock is present, it will retard the ignition timing to attempt to eliminate the knock. The ECM will always try to work back to a zero compensation level, or no spark retard. An abnormal KS signal will stay outside of the noise channel or will not be present. KS diagnostics are calibrated to detect faults with the KS circuitry inside the ECM, the KS wiring, the KS voltage output, or constant noise from an outside influence such as a loose/damaged component or excessive engine mechanical noise.

Elite..the confusion here is based on you not understanding what you have and what you are trying to read. Assuming you have a 97-08 V6 3.8L there is only one KR reading that you need to concern yourself with. If you are looking at the knock channel noise levels, then you should see the two seperate sensors. However it appears you are looking at the KR or Knock Retard reading, and in our cases we only have the one ICM and coils for timing, so retardation is only done in one place aka one reading.

I am looking at KR1, KR2, KR3 on the AF gauge & it seems only KR1 gives me a reading which now makes sense based on the explanations above. A few of my mechanic friends suggest that if detonation was in fact occurring, I should be able to hear it but I am not sure what to expect with a GP? I could hear detonation on the SN95 5.0's no problem.

I've driven 20 miles home from work with a bad lower end and almost zero oil pressure. KR was pegged at the max 15 degrees and I couldn't hear the bottom end noise until I hit the first stoplight off the highway. After that ...... no one within a half mile had any questions that I'd be swapping that motor

Depending on what/how..you might or might not hear it. I've never heard knock with my ear. I've seen it on a gauge though.

detonation sounds like popcorn.

and the only time you'll hear it is if it's really bad.

So if I assume I am not detonating because of a legitimate mechanical problem, can I still get the car custom tuned or is the KR reading an integral part of tuning?

Originally Posted by Elite6

So if I assume I am not detonating because of a legitimate mechanical problem, can I still get the car custom tuned or is the KR reading an integral part of tuning?

Get a wideband
Get a tune

Overkill is a short drive away, if my gauge reading KR (potentially not detonating though) is not a problem, I will drop off car with him for tune.

You really don't seem to understand this subject.

Please, be gentle and try to not get KR readings on your way to drop off the car. When you get it back, you shouldn't have KR anymore....because that's part of the tuning process.

Bill i dont understand your statement actually. My question is simple now: does a tuner need a kr reading to tune a car or can they rely on a wideband etc.. to tune instead. I drive my car 95% of the time pretty easy with 0 KR, my goal is not induce KR unless i am specifically trying to look at certain pcm readings during the kr reading. Car will be driven to overkill with 0 KR and we will see what it comes home at.

Car must have a knock sensor, how else is it going to know if it needs to retard timing and save the motor from blowing up.

Just because you see no KR when you are driving and nearly none at WOT doesnt mean you don't need one.


There are so many tables inside the PCM that deal with knock retard/abuse/torque mngt, so you can't remove them.