Mercedes G Klasse Diesel Engine Power Loss

Sounds like a lean condition alright. Reduced power and a rough idle, plus the check engine light screams fuel delivery problem. Is it just jerking during acceleration or all the time? Could be your fuel injectors are clogged or even failing. Have you checked for any error codes? Definitely don't ignore it!

It's mostly jerking when I try to accelerate. I haven't checked any error codes myself, not sure how to do that to be honest. Could bad fuel injectors really cause all these problems? And how difficult is it to check them?

Faulty fuel injectors can cause those symptoms. They're responsible for spraying fuel into the cylinders, and if they're not working right, the engine will run lean, which causes all sorts of issues. Checking them yourself can be tricky, you'll need some tools and knowledge. I'd recommend taking it to a workshop. They can properly diagnose the issue and replace the fuel injectors if needed. Otherwise you might end up chasing your tail.

Appreciate the advice. Took it to the shop, and you were spot on – turns out a fuel injector was defective. Got it replaced, and everything's running smoothly again. Total cost was around 515€, not cheap, but worth it to have the car running right. Thanks again!