Faulty Knock Sensor
 

Hi, my 93 WRX import has been running a rough idle and hesitation for a while now without any engine light coming on. Last week the engine light finally triggered and using the connectors under the dash I managed to get code 22 out of it which I believe is the knock sensor.

I took the old sensor out and it has 2 or 3 cracks through the plastic so I can safely assume its pretty terminal. Over the weekend I picked up a 2nd hand knock sensor from a Subaru breakers as I wanted to try and get the job done yesterday. Fitted it but it appears to make no difference, still got rough idle and engine light on the dash. I tried hooking up the diagnostic connectors under the dash again in an attempt to reset the ECU but this was still flashing up as code 22.

I have checked the voltage on the wire that the knock sensor plugs into and I'm getting 5 volts. When the knock sensor is plugged in I only get about 3 volts from the metal off the bottom of it.

So my question well questions are is that a normal reading? Should the voltage drop like that or is the sensor I picked up no good? Have I missed something with the ECU reset? Do I need to unhook the battery for 24 hours or is there an easier and quicker way to do it?

I am nowhere near an electrician but trying to learn the tricks as I go along so any help, hints, tips, kick in the right direction would be greatly appreciated.

Check out this thread which may help.
https://www.scoobynet.com/1007359-de...rol-map-2.html

Thanks, Welloil - there is some in-depth technical info in that thread. I've changed the MAF of a working car and that sorted the idle issue. I have also tried a knock sensor of a working car and ECU reset on mine but I still have the same issue with flatspots/hesitation/loss of power and code 22 is still showing on the dash.

I took a voltage reading on the connector the knock sensor plugs into and got 5v on mine but on a working 94 wagon import it only gave 3v. Could the higher voltage on mine be the problem? Could this be a short somewhere?

Either that or is code 22 a red herring and in fact the engine is just dying?

I had a duff knock sensor after my re-build , actually I think I damaged the cable (Homer forgot to disconnect when he pulled the engine) It was anyway a bit brittle through age/heat so it was no surprise after re-build that I had rough running intermittently, I tried a multimeter test method as well ( Out of the car I seem to remember 480 * changed if I waggled it ) I bought a new one from the stealership. Even when you fit it however the code / engine yellow light will stay on until you restart 3 times. Running fine now. Oh don't forget its supposed to vary a little bit if you knock it and you need to make sure its clean on the block as the white powder corrosion on mine after the build also stopped it from working right. Clean it with some engineers paper first.

For my MY05

Part number was 22060-AA100 , and it was 103 €uro from Häulser Frankfurt. I had no choice you cant pass a Tüv here without it running right.