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I have a 2000 Honda Civic iSR 1.6L D16Y8 MTX and the MIL comes on intermittently with a code for the knock sensor ( blinks out 23 when I short the code display pins ). The code goes away when the car is turned off. I can drive at high speed and rpms on the highway for hundreds of kilometers without it coming on, and then drive leisurely around the neighborhood at low speed around 2k rpms and it will come on for no apparent reason.

I recently replaced the engine, and don't know / remember if it was coming on before that ( since I bought it with a bad engine with the intention of replacing it ) , but I went ahead and replaced the sensor with a cheap one I got off aliexpress.

I followed the flowchart in the WSM:

enter image description here

and got to the circled box and was wondering exactly what they mean by, "system is OK at this time."

Can I assume that it is in fact a loose wire / bad connection someplace? Can I safely ignore this problem? Will the knock sensor going off intermittently like this affect my performance in any way? I know there is the issue that ignoring the MIL may mask another MIL, but beyond that is there any problem with ignoring it?

EDIT Sept. 18th 2016

I've been monitoring this for a few days, and some days it won't come on at all, and other days it comes on a seemingly random times, usually a few minutes after I start driving.

Edit Jan. 15th 2019

Just to follow up, I replaced the knock sensor with an inexpensive one off of rock auto that looked decent and since then the following has went away.

  • does it come on at random or is there a pattern to when the code sets? since you replaced the sensor, it's either a wiring or ecm issue. knock sensor circuit codes generally don't affect engine performance. – Ben Sep 11 '16 at 11:44
  • @Ben I just noticed something interesting. I changed my coolant from distilled water to standard green coolant and noticed that the MIL was going off less. The past few days, once it comes on, and I turn off the engine to clear it, it doesn't seem to come on again unless the car has sat for quite a while. I would even go so far as to say it only comes on when the engine passes some temperature threshold, and then it doesn't come on again as long as the engine stays above a certain temp. The engine doesn't cool off as fast with glycol coolant as it does with water, so it comes on less. Crazy? – Robert S. Barnes Sep 14 '16 at 14:00
  • "with a cheap one I got off aliexpress" been there done that. Wasted money. You'll need the OEM. – justinm410 Sep 14 '16 at 14:38
  • With P0325, if you just need to pass emissions in the short run, I've read you can connect microphone directly to the computer; this effectively "white noise" may satisfy the computer. Obviously, you should eventually get it fixed properly. – Tahlor Jan 14 at 20:02
3
  1. Cheap piezo knock sensors stink. I ended up paying for OEM on my Subaru.

  2. Make certain there's no debris or a loose fastener in the vacinity of the sensor. I had a random bolt rattling against mine on my Subaru.

  3. Make sure the contact area is very clean and flat. Mine was filthy and rusty on my Subaru.

  4. Follow the torque guidelines exactly. I just made mine "tight" on my Subaru, and that pre-stresses the crystal in such a way that it changes its frequency response. The correct torque was far less than I expected and specified in inch-lbs.

Bottom line, I chased a P0325 on my vehicle for months. I don't beleive there was anything else I could have done wrong. I pretty much made every mistake possible, but I suppose I learned a lot. Code has been gone for 3 years and probably 40k miles at this point.

  • So what would be the order in which you would attack this problem? It's quite possible my previous knock sensor was just fine. I had the guys who installed the engine put in the new knock sensor, and I'm pretty sure they didn't have any torque specs. – Robert S. Barnes Sep 11 '16 at 19:43
  • I'd follow steps 1 through 4, put the old one back, with a clean mating surface and the proper torque (if specified). – SteveRacer Sep 11 '16 at 21:53
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    in the end I ended up replacing the knock sensor with one off of RockAuto that looked decent but not too expensive and since then the problem has went away. – Robert S. Barnes Jan 15 at 10:35
  • Great! Only took 28 months?? – SteveRacer Jan 16 at 2:51

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