XC90 Engine Stalling at Idle

I had something similar happen with my old Mercedes-Benz C-Class. The check engine light and stalling at idle match what I saw. The diagnostic pointed to a bad fuel composition sensor. What specific error code is your scanner giving you? Has the fuel filter been checked for contamination?

Thanks. The error code is P0172, which says the fuel mixture is too rich. I haven't checked the fuel filter myself. Could a bad cable or plug connection cause a false reading like that?

P0172 does mean a rich mixture. A bad cable or plug on the fuel composition sensor itself is possible. I'd check the wiring and connections carefully before replacing the sensor. Based on my experience, and given the error code, it might be worth having a qualified technician take a look. It could save you some money. My Mercedes issue turned out to be a faulty sensor connector.

Thanks a lot. The info about the sensor connector is really helpful. I made an appointment with the workshop for a full inspection. They found a defective cable connection, and after they replaced it, the fault was gone. Total cost 95€.