knock sensor operation

[mhoult 0]

I have a fault flagging up stating:

 

00540 - Knock Sensor 2 (G66)

31-10 - Open or Short to Ground - Intermittent

 

To check it is the one at the front of the engine i disconnected it and ran vag-com with the engine running. No faults were found. I did the same with the rear one with the same result. The water temp was 85 so the sensors should be active.

 

Can anyone explain this?

 

Can you access the direct reading of the sensor from vag-com?

 

Thanks

[dr_mat 0]

Using my psychic powers I think you have a VR6 (two knock sensors, see).

The ECU is pretty stoopid, that's the best explanation. Try shorting the wires and see if an error code gets thrown.

Don't think you can get a measuring block that reads values from the knock sensors, cos after all they're not linear measuring tools, they're simply microphones.

[Ice White Socks 0]

couldn't it just be that you have knock sensor which is slowly giving up the ghost? maybe working a bit of the time and then conking out- its something ABS sensors do for fun. The ECU would store the fault code even if it went out of range just once- but i bet both were working fine when you checked them.

 

I would clear the fault codes, run for another week and then check again. If it flags a problem again you'll probably need to replace them both

 

Mike