Mercedes G Klasse coolant loss and engine light

I had a similar issue with my older Audi A4 a while back. Coolant disappearing, engine light on. I was pulling my hair out trying to find the leak. Turns out, it wasn't a leak at all! The water pump was faulty, and it was leaking internally. The coolant was getting burned off. Have you checked the water pump? Also, did you pressure test the system? That's how they found my issue. It might be worth looking into before you start chasing electrical gremlins. It could also be a cracked head gasket, but let's hope it is not that.

The water pump issue is a novel consideration. I had not contemplated an internal leak. Regarding the pressure test, could you elaborate on the procedure? And what were the specific symptoms you observed with the faulty water pump beyond the low coolant level?

The shop hooked up a pressure tester to the coolant reservoir, basically pressurizing the system to see if it would hold. If it doesn't, that means there's a leak somewhere. As for the symptoms, besides the low coolant and the engine light, I noticed the temperature gauge would fluctuate a bit, especially when idling. Sometimes it'd creep up higher than normal. Honestly, I'd recommend taking it to a trusted mechanic. They have the right tools and know-how to diagnose this properly before you throw parts at it. But tell them about the water pump. At least they know where to start.

I have since taken the vehicle to a workshop. It was indeed a defective cable. The repair cost was exactly 95€ as anticipated. I appreciate your assistance.