GLK transmission issue resolved

Sounds like a potential electrical issue affecting the transmission control. Before replacing the radiator oil pressure sensor, have you checked the transmission fluid level and condition? Low or contaminated fluid can cause similar symptoms. Is the car overheating, or are you just concerned? A faulty temperature sensor could also trigger some of these issues. Is there a possibility the oil cooler is damaged?

Thanks for the insights. I haven't checked the transmission fluid level because I'm hesitant to tamper without proper diagnostics. I'm not sure if the car is overheating, but I am concerned. Is there a straightforward way to assess the temperature sensor or perform leak detection without specialized equipment?

A visual inspection for leaks around the oil cooler is possible, but assessing the temperature sensor and fluid level accurately often requires diagnostic tools. Given the grinding noises, emergency mode, and error codes, it would be prudent to have a qualified technician inspect the system before further driving exacerbates any underlying mechanical damage. It's difficult to say definitively without hands-on inspection, but it sounds like you could be facing more than just a simple sensor issue.

I appreciate your guidance. I took the GLK to a workshop. The issue was a corroded connector on the radiator oil pressure sensor, as suspected. The repair, including connector replacement and error code clearing, was 95€. Thanks again for confirming my suspicion and recommending professional diagnostics.