Knock sensor for an N/A.

[rnoswal]

I get the 52 code, knock sensor. I tried another sensor, but the same thing. I went to ebay and bought one that the seller said presented no codes, I got the 52 after installing it.

I checked the wire from the sensor to the ecu and got continuity. Inoticed that as the wire leaves the ECU, it picks up a grounded shroud which I assume continues through the firewall and goes almost all the way to the sensor. The wire at the sensor on my car comes out of the harness just as a single wire and plugs into the sensor.

I have looked in the manual to see if there is any type of manual check that can be done on the sensor, but I find no resistance values or anything. I have an A/T ecu and a M/T ecu. They both throw the same codes.

Is there a reading that can be taken on the sensor? I put an ohm meter on it and it reads as an open. All three read the same. I have been trying to find a voltage reading that comes out of the ECU but again nothing.

All this seems to be is a sensitive noise detector for detonation and gets read as noise and the ECU takes that and retards the engine timing untill it goes away, but I am sure there is more than that involved.

So, anything on a value that can be read with a meter on the sensor? Anything that I might look for with the wireing. Like I said, it has good continuity from the ECU to the plug, just not sure about grounded shroud around that wire.

I hate that engine light being on, but I need it in case there are other problems ever.

Thanks
Russ

[joel w]

i wish i could help but i did steal this off another site, it was interesting to me.. specially the second paragraph..


Knock sensors are nothing but heat resistant microphones. The signal from a knock sensor is an audio signal recording engine noise. The knock detect circuit in an ECU first of all looks at that audio signal ONLY during about 5 deg ATDC to about 70 deg ATDC, where knock is most likely. The characteristic audio signal for knock has a specific frequency (pitch) that the knock detect circuitry filters out. This pitch (some frequency between 5 kHz and 20 kHz) is dependent on bore size, average gas temp in the chamber and comb. chamber shape. The knock detect circuit is factory tuned for that. On many OEM ECU's the knock circuit is switched off above ~4000 RPM, because the knock signature signal gets buried in other engine noise.
Engine mods like boring out, turbo's added, different boost, different fuel and so on, can change the characteristic knock frequency with the result that the ECU will listen to the wrong frequency and will not detect knock at all with it's existing sensor. I can also pick up other engine noise as knock.
There are products out there that attempt to detect knock from existing knock sensors. They typically require you to program a threshhold amplitude level for the knock signal by RPM, without regard to the characteristic knock frequency of the engine. That works only very marginally, because if the knock sound level is above the engine noise level at higher RPMs, you can hear it already with your ears before that circuit can detect it and you might already have engine damage.

Regards,
Klaus


found this too, maybe its a common problem..
http://www.supras.com/06/techcenter/display.php?QID=69

[rnoswal]

Thanks Klaus! That is a very good article. I will try what is written in that and see how it works.


Thanks again

Russ