[urq] Knock sensor ?

dgraber460 at aol.com dgraber460 at aol.com
Mon Oct 27 13:59:59 PDT 2008

Sorry for not being more?specific in the original post.
I was referring to knock/ping sensors bolted to the block. Not the NOx sensors in the exhaust stream.
It appears that one part number fits a large number of models through the early 90's including cylinders 4,6,8, turbo and NA. So I'm thinking the answer to my question was yes it will work.
Any knowledge to the contrary would be appreciated soon, as I will probably install it tonight and with the 3B in the URQ chassis, one must remove the radiator to access and properly torque the little bugger.
Thanks to all that replied (and might yet respond).
I love these lists! Couldn't own these cars without them.

Dennis Graber
Denver, CO

-----Original Message-----
From: Geraint Lloyd <geraintlloyd_qc at yahoo.ca>
To: urq at audifans.com
Sent: Mon, 27 Oct 2008 12:10 pm
Subject: Re: [urq] Knock sensor ?

Are we talking about ignition knock sensors or NOx sensors?

I would guess that knock sensors would only differ in terms of mountings and
At the end of the day, pinking is pinking and sounds pretty much the same in
any engine. Or rather, I have a hard time imagining that a PZT crystal could
be tuned for a specific engine's knock as the knock would be over to broad a
frequency band. It is audi(o) after all. In terms of crystal size, I can't
really see that making a huge difference either. I would expect the
filtering to be done in the ECU so maybe crystal type would play a role in
terms of what signal amplitude, the ECU expects. I don't think that the
Knock sensor "trips" when there is knock, it just listens and generates an
electrical signal at the same frequency that it vibrates at. And it's easy
enough to make a specific notch filter for each engine in the ECU

I don't think that we are at the level of wanting to optimise tone, like
having an SM57 on the snare drum and an SM58 for vocals.....

But then I could be wrong


A Geophysicist

-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] On
Behalf Of Louis-Alain Richard
Sent: 27 October 2008 13:12
To: 'Tony Hoffman'; dgraber460 at aol.com
Cc: seiche at shadetreesoftware.com; urq at audifans.com; quattro at audifans.com
Subject: RE: [urq] Knock sensor ?

Non expert here. A knock sensor is a mike that listen the engine. While they
are all the same electrically, I guess that each different unit is tuned to
listen to some specific frequencies, different from engine to engine. That
could explain the different part numbers, and explain also why some units
work perfectly on different engines : you can install a less sensitive knock
sensor on a smooth engine, but the opposite  will trigger some codes more
easily I guess.

My 0.02,


-----Message d'origine-----

I've done it before, on a V8Q. Had a bad one, used a known good one
from a 5000TQ. It cleared the code, so I'd assume there's not a
problem with switching them. Since they are all basically a
piezo-electric crystal designed to generate voltage at a given
frequency, I don't see why there would be a difference.

However, without a dyno (before and after runs) I can't be 100% sure.

Perhaps someone out there has more info, but until then, I'd certainly
swap them out and see if that clears the code. It can't hurt anything.


On Sun, Oct 26, 2008 at 6:01 PM,  <dgraber460 at aol.com> wrote:
> Any experts (or non experts) know if knock sensors can be exchanged across
> I'm trying to diagnose why I'm getting a sporadic check engine light?in my
recent 20V 3B motor in my URQ. The knock sensor with a suspect wiring at the
block has a part number of 077-905-377A (& 0261-231-040).
> The code stored earlier, and cleared was "00540 003 - Knock sensor (KS)
2-G66 No signal".
> A sensor I picked up yesterday at the breakers [an MC engine I believe]?is
034-905-377A (& 0261-231-004).
> Can these be interchanged?
> Yes - the one on the motor was torqued to spec.
> Dennis Graber

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