Mercedes S Klasse VANOS problem

VANOS issues are common on these engines. Have you checked the timing chain? A stretched chain can throw off the timing and cause similar symptoms. Also, inspect the wiring harness to the camshaft solenoid valves for any damage or corrosion. Have you noticed any unusual noises from the engine?

I hadn't thought about the timing chain itself. I will check it. When you say unusual noises, what specifically should I be listening for? Is there any way to check the solenoid valve without just replacing it?

Listen for a rattling or ticking sound, especially at idle, which could indicate a worn timing chain tensioner. As for the solenoid, you could try swapping the inlet and exhaust camshaft solenoid valves to see if the fault code changes. If it does, the solenoid is likely the culprit. Otherwise, the issue is probably something else. But honestly, at that point I would bring it to the workshop.

It was the inlet camshaft solenoid valve, as suspected. Replaced it, cleared the codes, and everything seems to be running smoothly again. Fuel consumption is back to normal. Total cost around 250€. Thanks again.