Citroen C2 Automatic Transmission Issue

From your description, it certainly sounds like the transmission oil temperature sensor is the primary suspect. The symptoms you describe, such as the warning lights, emergency mode, and unclean shifting, are consistent with a faulty sensor. These sensors are crucial for the gearbox control unit to function properly, as the TCU needs the oil temperature to properly adjust the shifting behavior. Have you checked the transmission oil level recently? A low oil level can cause the oil to overheat, which could also trigger the sensor and produce similar symptoms.

I haven't checked the transmission oil level myself yet. I was under the impression that checking the transmission oil level on these automatic gearboxes could be a bit tricky and potentially require specialized tools or knowledge. Is it something that can be easily done at home, or would you recommend taking it to a workshop to have it checked professionally? Also, if the oil level is indeed low, could that be the sole cause of the sensor malfunction, or is it more likely that the sensor itself is faulty and needs replacement regardless?

Verifying the oil level on your specific gearbox can be a bit challenging without the proper tools and knowledge. If you're not comfortable doing it yourself, I'd strongly advise against attempting it, as you could potentially cause more harm than good. Given the symptoms and the error code, it's highly probable that the low oil level is the root cause of your problems. In your particular case, the grinding noises during shifting are also a clear sign that the oil level is too low. However, a faulty sensor can also trigger similar issues. Given the circumstances, I would recommend consulting with a qualified workshop to properly diagnose the issue and perform the necessary repairs.

I followed your recommendation and took my C2 to a local workshop. They confirmed that the transmission oil level was indeed critically low, which was causing the sensor to report incorrect readings. After topping up the oil and replacing the sensor, the issues seem to have disappeared entirely. The gear shifts are now smooth, and the warning lights are gone. The total repair cost came out to 365€, which I consider a reasonable price for resolving the problem. Thanks again for your valuable help!