I fill up only with high octane premium gas. When starting the engine and when it's not warmed up, it makes that knock-knock-knock-knock noise.
It shouldn't knock in the first place since I use premium gas, AND the knock sensor isn't working. What's up with that? I have 2008 X5 3.0 with 4000KM or 2500Miles on the odometer.

Is this going to hurt my engine if I don't go to the service center right away? It's difficult for me to make time to go and get serviced right now...