Faulty Knock Sensor
#1
Scooby Newbie
Thread Starter
Join Date: Sep 2014
Location: Wolverhampton
Posts: 16
Likes: 0
Received 0 Likes
on
0 Posts
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.
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.
#3
Scooby Newbie
Thread Starter
Join Date: Sep 2014
Location: Wolverhampton
Posts: 16
Likes: 0
Received 0 Likes
on
0 Posts
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 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?
#4
Scooby Regular
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 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?
Last edited by Linksfahrer; 14 October 2015 at 07:54 PM. Reason: * Was ohms on multimeter not volts
Thread
Thread Starter
Forum
Replies
Last Post
Mattybr5@MB Developments
Full Cars Breaking For Spares
28
28 December 2015 11:07 PM
Mattybr5@MB Developments
Full Cars Breaking For Spares
12
18 November 2015 07:03 AM