Movano Water Sensor Fault

Rough running and a water sensor fault on a Movano usually means a dodgy connection somewhere. Has the van had any recent work done, or been pressure washed near any of the wiring? Common issue points are the sensor plug itself and the wiring loom where it runs near the chassis rail. A wiggle test of the plug might show something up, but be careful, the pins are fragile. I'd also check the relevant fuses as a precaution.

How do I do the wiggle test on the plug safely, to not damage the pins? Can I diagnose this electrical fault with standard car diagnostics tools?

Wiggle test: gently move the connector around while the engine is running, or the ignition is on, and see if the engine note changes or the light flickers. As for diagnostics, yes, a decent OBD2 scanner should pull the fault code relating to the water sensor. That will confirm the initial fault. But sometimes, you need an oscilloscope to check the signal from the sensor is clean, or a multimeter to check the wiring. Honestly, given the potential issues, your best bet might be a workshop, the repair won't break the bank and it will give you peace of mind.

I took the car to the workshop, and it was a defective cable/plug connection to the water sensor, like you said. The repair cost 95€. The issue is resolved. Thanks again.