Knock sensor will show up if completely done for. Mine was gone (plastic casing cracked) but still did not really have any pinging but then again ran my old Golf (2.0 2E) on 25-30% E85 blended in with 95 petrol, so higher than normal octane rating.
If you have a 2.0 8v you can use 054 905 377 A instead of the one you have now, cable is longer other than that pretty much the same - however much cheaper!