Knock Sensor testing / resistance?
 

Hi,

First post, apologise for not introducing myself or uploads pics of the car yet but I'm at work at the moment.

I have a late 98 Classic turbo 2000 (MY99 i think, has all the MY99 parts anyway). Every now and then the CEL comes on. The fault code is the Knock Sensor. I reset the ECU and thought it was OK, until the next morning where on starting the car it lit up again. I tried emptying the tank, filling with 99 ron and resetting the ECU and it lasted longer before seeing the light come on after normal driving.

I have also tried cleaning the MAF sensor as I have heard this could make it run lean/ ping causing the CEL to come on for knock. This didn't seem to make much difference although resetting the ecu after cleaning the MAF did cause the engine to stall whilst driving along at 30mph after about 2 minutes - very worrying as the power steering and brakes go pretty quickly! It did start up again after a few goes then drove exactly how it used to.

I have measured the knock sensor on a good fluke multimeter to be about 20M Ohms, which seems very high, does anyone else know what it should be, or have any ideas how to fix the problem once and for all?

I did take one spark plug out (too time consuming to take them all out!!) and it had no soot or black on it at all (lean ?), nothing like the peugeots I've had in the past. I can also get about 28-30mpg with a mix of driving, but all 25 mile+ journeys.

Any ideas much appreciated.

Cheers,

Matt

the knock sensor is a microphone and will probably have a high impedance.

If your car is a 99 model, the MAF's are very fragile. so worth changing, about £80 from dealers.

You can do a simple test to check the maf.

Disconnect the connector to the maf when the car is idling. It should stall the car, but if it maintains any form of idle then the maf is suspect.

Not a fool proof method, but a reasonable indicator to a dodgy maf.

Andy

Cheers I'll try that tonight.

I forgot to mention that the CEL always goes off after about 10-20 seconds, but that disconnecting it did leave the light on permanently which would suggest that it is working or does work to some extent!

It does perhaps suggest its the MAF so I'll give that a go. Does anyone know what sort of voltages should be on which wires in the connector or is it best just to replace as a matter of cause?

You should see approx 1 volt at idle on signal pin from maf. 5 volt supply to maf and a ground pin

Thanks very much, all the info I was after.

Still having problems....
 

Raising an old thread but I still haven't fixed the problem.

Ocassionally the CEL light comes on with the 22 knock sensor error code.

I tried replacing the sensor with the bocsh equivalent everyone seems to use and the light came on all the time. Went back to the old sensor and it went out. Used a bit of injector cleaner and put 99ron petrol in and its just come back on again after 90 miles. Each time it comes on its only for 10 seconds, and only once has there ever been a drop in power at the same time (that was on crap fuel).

I have checked the MAF and have used Rom raider to log params but they all seem fine. Inj duty goes up to 67% on full wack (std uk turbo 2000).

As I noted in a thread before though the narrowband O2 voltage doesn't go above 0.92v so it's still possibly a little lean although I know you can't rely on it!

So whats going wrong guys? Is the knock sensor circuitry dying in the ecu? Is it running a bit lean? Interestingly the light only ever comes on, on light engine load, today when it was idling.