knock control on AQG

oldnick · #1 25th October 2016, 11:44 AM

knock control cyl 7 P1331 reg limit exceeded intermittent is the fault code I am getting

is there really a separate sensor on each cylinder ?
being a simple fellow I thought there was a sensor per engine or at most one per bank so what is this about and what to do ???

there must be some info about but can I find it ? can I ******

Ameiseuk · #2 25th October 2016, 04:07 PM

I thought there was one on each bank of cylinders?

mattylondon · #3 25th October 2016, 05:57 PM

Quote:

Originally Posted by Ameiseuk

I thought there was one on each bank of cylinders?

Yes, that's my understanding as well.

MikkiJayne · #4 25th October 2016, 11:01 PM

Yes, one per bank, but the ECU knows which cylinder it just fired so it can work out which one just knocked as well.

There are measuring blocks for individual cylinder knock detection parameters iirc so you can watch it running and see what is happening, and plot it on a graph using VCDS. Swap the coil pack and / or spark plug to another cylinder to see if it moves.

Ameiseuk · #5 26th October 2016, 05:27 AM

Quote:

Originally Posted by MikkiJayne

Yes, one per bank, but the ECU knows which cylinder it just fired so it can work out which one just knocked as well.

There are measuring blocks for individual cylinder knock detection parameters iirc so you can watch it running and see what is happening, and plot it on a graph using VCDS. Swap the coil pack and / or spark plug to another cylinder to see if it moves.

Ah, thats how it works...very clever.

oldnick · #6 26th October 2016, 11:56 AM

[quote=MikkiJayne;118912]Yes, one per bank, but the ECU knows which cylinder it just fired so it can work out which one just knocked as well.

There are measuring blocks for individual cylinder knock detection parameters iirc so you can watch it running and see what is happening, and plot it on a graph using VCDS. Swap the coil pack and / or spark plug to another cylinder to see if it moves.[/QUOTE

aha BUT
looking for parts it seems there are what are called blue sensors and green sensors ...presumably should be the same on each bank?

if I read this correctly the problem can be either

spark plug , coil pack OR knock sensor ?

tks MJ

MikkiJayne · #7 26th October 2016, 01:26 PM

S8s use 2 green sensors. One is in the V under the inlet manifold and the other is just behind the power steering pump. The 4-cylinders use one blue and one green.

I would say spark plug most likely, then coil pack, then excess carbon in that cylinder causing local hotspots and pre-ignition, then knock sensor. If it was failing one bank then sensor first, but since its one cylinder look at cylinder-specific things first