Mercedes GLK diesel function restrictions

Function restrictions can be a pain. When you say your phone won't connect, is that via Bluetooth or some other Mercedes connectivity feature? Does the error memory provide a specific code? Also, have you checked the vehicle's main battery? Low voltage can sometimes cause issues with the ignition system and various electronic modules, even if the engine starts fine. It can trigger malfunctions. Brakes, transmission, and suspension usually have nothing to do with it, but it's worth checking all the basics.

Bluetooth is the problem. I don't have the error code unfortunately. Where would I find the battery voltage reading? Can I check that myself, or do I need to take it to a shop?

Bluetooth connectivity issues, paired with error codes and function restrictions, can stem from the central communication module. A weak battery can introduce gremlins into the system. You could potentially check the battery voltage with a multimeter if you have one; most auto parts stores can test it for you, too. However, given the error and Bluetooth issue, it might be worth having a workshop take a quick look to read the specific code. It could save you time and potentially identify a more serious underlying problem. Since it's an error related to the multimedia system, it is separate from suspension, brakes or transmission concerns.

Thanks for the insight. I took it to the shop. It turns out it was indeed a pairing issue, but it needed a reset. It cost 45€ to sort it. It's all good now.