if you got a code for the knock sensor, then the ecu is reporting it faulty, non responding or reading way out of whack. That means usually that the sensor itself is faulty, especially if not in conjunction with other codes.
OBD is a diagnostic system to identify sensor or control faults, not to inform of running conditions in general but as a system check of all sensors.
The noise you describe may be getting picked up by a knock sensor, but that wouldnt trigger a knock sensor code, instead something like timing retardation figures in the ecu would change, the cel might come on for max timing retard reached but the code would be like "reading out of range", if its a fooked sensor of any kind you get "implausible signal or open circuit" type of codes (im generalising of course)
A knock sensor is a wee microphone and so can go open circuit, triggering a knock sensor error code. You should be able to check it with a basic ohm meter on low range - say up to 100 ohms. Any reading means its ok, its a little voice-coil so goes open circuit if faulty. This mic picks up sounds and that signal is fed thru a filter in the ecu analog inputs to look for the sounds of pinking or pre-ignition which have a specific range of frequencies that are known to be emitted from the cylinders when knock occurs. If knock is detected, the timing is retarded until it stops, or hits the limit. Then it goes to limp mode if the limit is reached, I know scoobs can pick up noise from a new oilfilter not filled yet on first start and trigger timing retard, possible wi the golf i suppose for other noises but unlikely as they are pretty accurate when working.
If the KS is showing as missing or faulty to your ecu, it will pull the timing back and go into limp mode as it cannot determine correct max timing advance any more.
Hope this helps mate
