C Klasse Oil Temperature Sensor Problem

I had a similar issue on my C Klasse. Same symptoms: oil temp warning, code thrown, and the oil pressure light. Before chasing wires, did you scope the sensor's signal with a multimeter or an oscilloscope? A flaky sensor can act like a wiring issue. Also, check the sensor's resistance when the engine is cold and warm. Does the resistance change smoothly?

Good call on scoping the signal. I haven't yet, because I suspected the harness. When this happened to you, did the error code point to the temperature sensor, or was it more generic, like a CAN bus error? Do you remember the resistance values when you checked?

The error code was specific to the oil temperature sensor - something like 'Oil Temperature Sensor: Implausible Signal'. I don't remember the resistance values. Since you're getting the oil pressure light intermittently, and if the sensor signal checks out, inspect the oil pump. But since my experience was similar, and the error code is specific, I'd guess it's a faulty sensor or wiring near the sensor. If you can't figure it out, take it to a workshop.

Appreciate the input. You were right. I focused on the sensor and its connections and found a corroded pin in the connector. I cleaned it, added dielectric grease, and the error is gone. Total cost: 95€ for the sensor. Thanks for the help. Sometimes the simplest things are easy to miss.