After spotting some oil on the driveway and nothing seemed to be out of the norm, mechanically, I decided to take VSAG-COM out and give the car the quick once over...

2 Faults Found:

16804 - Catalyst System; Bank 1: Efficiency Below Threshold

P0420 - 35-00 - -

16712 - Knock Sensor 1 (G61): Signal too High

P0328 - 35-10 - - - Intermittent

Readiness: 0000 0000

I did clear the codes and they have not returned yet after an engine turn off then on again. I've yet to take it for a spin.

What should I look out for with the above faults? (What does the knock sensor do anyway?)

16804/P0420/001056 - Ross-Tech Wiki

16712/P0328/000808 - Ross-Tech Wiki

The knock sensor senses vibrations from the engine, particularly vibrations caused by the fuel igniting before it's supposed to. If it senses a vibration it will send a signal to the ECU that will in turn retard the ignition timing, which will take the edge of the performance.

Fuel pre-ignition can be caused by the ignition timing being too advanced, an inferior quality fuel and not so much found theses days - excessive carbon build up in the combustion chambers, leading to a higher compression ratio and hot spots. I have known a 8 valve Fabia suffer from reduced performance caused by a rattling timing chain setting off the knock sensor.

Thanks fordfan.

I was thinking I had a tankful of dodgy petrol recently, but the car was much more lively once a new tankful of petrol was put in. I think it's time to treat the car to a tankful of v-power to clean out the pipes!

I have the same two codes show up at the same time. I can't figure out why they are on simulataneously.