Coolant Level Issue on Mercedes GLS

Whoa, that sounds eerily familiar! Had almost the SAME thing happen with my old Volvo a while back. Check engine light, coolant warning... It was a freakin' nightmare! You said you checked the cap, but did you really give it a good look? Mine looked fine, but it was actually cracked underneath where you couldn't see it. And yeah, could be electrical, but don't rule out a tiny coolant leak somewhere. I was pulling my hair out trying to find mine!

Thanks for the input. Regarding the radiator cap, could you elaborate on what specifically I should be looking for besides obvious cracks? Were there any specific areas that were more prone to failure on your Volvo? Also, if it was a minor coolant leak, where would you recommend checking first? I'm trying to avoid a lengthy and expensive diagnostic process if possible.

Okay so with the cap, look really close at the rubber seal part. Mine was hard and brittle even though it looked okay. As for the leak, check around the hoses that connect to the radiator and the engine block. Also, and I'm just saying this because it happened to me, check the weep hole on the water pump. Honestly, though, with a Mercedes, you're probably better off just letting a mechanic take a peek. I was sure I could fix my Volvo but I just ended up stressed lol.

Thank you for sharing your experience and providing those pointers. I took your advice and had it checked by a professional. Turns out it was indeed a faulty coolant level sensor connector. They replaced the connector, and all is well now, just like the diagnostic suggested. The repair cost was indeed around 95€. I appreciate you nudging me towards a proper diagnosis instead of chasing potential water pump or head gasket issues!