Ccrosser Transmission Oil Temperature Sensor Issue

This sounds like a serious issue with the automatic transmission. The symptoms you described, combined with the error code, certainly point towards a problem with the transmission oil temperature sensor, potentially triggered by low oil level. Have you checked the gearbox oil level recently? Is it possible there's a leak?

I haven't checked the oil level myself. I'm not really sure where to even start with that! Whereabouts would I find the transmission oil level check? And is there a specific type of oil I should be using if I need to top it up?

Given your lack of experience with checking transmission oil levels and the potential complexity of the issue, I would strongly advise against attempting to diagnose or repair this yourself. Incorrect fluid levels or the wrong type of fluid can cause significant damage to the automatic transmission. The grinding noises are another red flag. I suggest taking your Citroen to a qualified workshop as soon as possible to have it properly inspected and repaired.

Thanks for the advice! You were spot on. Took it to a workshop, turns out the gearbox oil was really low. They replaced the faulty temperature sensor and topped up the oil. Cost me 365€ but shifts are smooth again. Appreciate the help!