My 2015 Holden Captiva makes a knocking sound

What you haven’t told me is whether your car is a petrol or diesel Captiva. The two engines have very different ways of operating and both can make very different noises depending on what’s going on with them.

Diesel engines often have a fair bit of fuel pump noise which can increase as the car travels more kilometres and the pump develops a bit of wear. But whichever engine we’re dealing with, if the noise is at idle, then you’d really want to check the engine’s oil pressure. Oil pressure is lowest at idle, and low oil pressure can cause noises from the hydraulic lifters and even the engine’s crankshaft and pistons. Neither of those are what you want to hear, though, as they suggests some fairly major internal wear or damage.