[s-cars] Re: Knock sensor failure?

[Michael Wakefield]

For what it's worth, the following is from an Audi publication I have 
(WSP-521-218-00). It describes the function of the knock sensors, and 
more importantly says that the only
way it will throw a code is for no signal. Unfortunately, it does not 
address installation torque issues.

"Cylinders 1, 2, and 3 are monitored by knock sensor I (G61), and
cylinders 4 and 5 are monitored by knock sensor II (G66).

Signals from the knock sensors are used by the Motronic control module
for cylinder selective knock control.

The ignition timing of an individual cylinder can be retarded if knock
is detected. If knock continues, a richer fuel mixture will be used and
the charge pressure is reduced.

Knock control is adaptive, which means that the system will adapt to
fuel quality and driving conditions.

Self-diagnosis recognizes one fault which is "no signal".

If a fault develops with either of the two knock sensors, the ignition
timing will be retarded by 11 degrees and the fuel mixture will be
enriched."

Mike Wakefield
Highlands Ranch CO
93S4
97Cab

On Apr 1, 2004, at 4:36 AM, Mihnea Cotet wrote:

> Phil, I must say I don't agree. I've BTDT in a few cases where the 
> knock sensors had been overtorqued and the only effect this had is 
> that the ECU wasn't seeing any knock activity when the engine was 
> pinging like a churchbell. There are a few maps that the ECU is using 
> in case of knock sensor activity in a 20vt ECU and I'm sure I know 
> where they are and what they mean, and the ECU didn't give a damn 
> about them although you could hear the engine pinging very audibly 
> even in 3rd gear (where the load is a lot lower than in 6th gear for 
> instance).
>
> Just my 0.02,
>
> Mihnea
>
> At 09:08 1/04/2004 +0200, Phil Payne wrote:
>
>> > I'm sure that knock sensors have failed from time to time but I 
>> would
>> expect that the normal failure mode would be that it simply stop 
>> putting
>> out a signal.  However, has anyone experienced a knock sensor failure 
>> in
>> which the knock sensor becomes overly sensitive and reports knocking 
>> to the
>> ECU when none is actually happening?
>>
>> Yes, if it's overtorqued.
>>
>> --
>>   Phil Payne
>>   http://www.isham-research.com/quattro
>>   +44 7785 302 803
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