1. Home
  2. Subaru Cars Forum
  3. Check Engine Code=Knock Sensor, Could it be a false indication

Check Engine Code=Knock Sensor, Could it be a false indication

I'm not a DIY'er, but I want to not throw money away at possible wrong repairs.

1997 Legacy 2.2l

6 months ago my check engine light came on and the code read at Auto Zone was "Knock Sensor" It was suggested that the part could be faulty, could be a wiring short (intermittent). The check engine light comes and goes. It almost always comes on after 1/2 hour or so at highway speeds. I've never notice it go out while driving once it comes on, but sometimes it's just off when I turn the car on again. I've never heard knocking under heavy acceleration when the light is on.

My question is whether that particular check engine code is prone to indicating failure in a component which is incorrect, ie something else is wrong (and whatr that might be). This sounds like around a $200 mechanic repair (diag, part, labor). It's not a lot, but I'd like not to have the same code pop up again after installing a new part.

TIA

Reply to
kaplan3jiim
Loading thread data ...

Check the connection to the knock sensor. I've had a loose connection there throw a knock sensor code before. Removing the connector and reattaching it solved the problem. Since you don't mention either way, if your Legacy has a turbo, ensure you are burning the proper fuel as per the manual.

~Brian

Reply to
strchild

In addition to the post about wiring, a vehicle that age could also have some carbon deposits built up in the engine that might make it a little more likely to exhibit knock - particularly after 1/2 hour at highway speeds. And you could try experimenting with higher octane gas. If the problem persists at the same rate as with lower octane - I'd suspect an intermittent knock sensor. If the problem goes away - possibly carbon deposits or ???

Carl

Reply to
Carl 1 Lucky Texan

Try high octane gas, if the light goes out, then the knock sensor is doing its job by detecting the knock. If it does not go out, then it could be a bad sensor or some other problem with the sensor. Or some other engine component knocking and the sensor is legitimitely letting you know.

Reply to
dnoyeB

I lean to think that the sensor is just doing it's job.

The light should go off after 2 or 3 trips with no fault.

Are the spark plugs of the right temperature range? You can take them out and see if there is carbon build-up. When the carbon gets hot, it changes all the dynamic in the cylinder. Check the gap and ignition timing too (even if the latter cannot be adjusted).

The fact that the sensor alerts you after 1/2 hour indicates it could be engine temperature related.

I doubt the problem is caused by the fuel/air ratio because the codes would be different.

Try using different fuel as dnoye suggested

Good luck

snipped-for-privacy@comcast.net wrote:

Reply to
AS

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.