Scenic check engine light and fuel consumption

I had similar symptoms on my old BMW 3 series. Check Engine Light, poor fuel economy, the works. Turned out the VANOS solenoid was gunked up with oil sludge. Have you checked for oil sludge buildup? It can cause the solenoid to stick and throw off the timing. Also, have you checked the VANOS solenoid power supply?

Interesting, thanks for the quick reply! Oil sludge is a good shout, I hadn't considered that. Where exactly should I be looking for the sludge buildup, and how would I check the VANOS solenoid power supply?

On the BMW, the sludge was pretty evident when I removed the VANOS solenoid itself. It was coated in thick, black gunk. As for the power supply, a multimeter is your friend. Check for voltage at the solenoid connector when the engine's running. If you're not comfortable doing that, it's probably best to have a workshop take a look. It's likely a defective camshaft solenoid valve or an issue with the power supply.

Thanks a lot for the advice! I'll check for the sludge and the power supply, but you're right, if I can't figure it out I'll take it to a workshop. I got a quote for around 250€ which seems reasonable. Appreciate the help!