Re: Knock Sensor Question

[D Kunnath <djktno@engin.umich.edu>]

> >          My problem seems to be quite a bit different than Craig's...only
> > getting one set code (43 EST), and it's intermittent.
>
> Might just be the ESC no longer triggers at the self test, in an expected
> manner.  ie the self test isn't adding quite enough advance, or the sensor
> is going deaf.

So there is a possibility that I have just a bad sensor???  Any way people 
out there know how to test it off the car?


> >          Knock counts on the scan tool after a 20min hot engine drive
> > counted no more than 6.  When the driver would accelerate, the knock
> retard
> > was up to 20deg right away...never more that 20, never less.  Different
> > starts (more / less pedal) produced the same timing retard.
>
> 20 knock counts or 20 degrees?.  Just off hand haven't seen a ship with 20d
> retard allowed.

Scan tool showed 20 degrees of timing retard...it read either 0d or 
20d.  Knock counts were between 3 and 6 for my 10-20min test 
runs.  Probably did 5 runs that day, each from a cold start That was last 
Saturday (car is in exact same configuration now).



> >          I even took the "advice" of my GM service manual and went through
> > the flowchart for the ESC system to test the knock sensor with an AC
> > voltmeter, but I never saw *any* AC voltage from the sensor.
>
> Neither have I.

Never seen AC voltage from sensor?  Manual said to check for this.  Do you 
say this because you think this would be an impossibility, or the AC 
voltage is so small?

I guess I may have to pull the plugs to check them out with a careful eye 
to see if there are any more signs before I try to move on.

If there is some kind of inaudible knock really happening, what kind of 
steps might I take to correct this problem?

DK



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