Citroen C4 1.6 HDI

Hello everyone.
I bought a C4 of embargo, I could make a diagnosis and give me failures in the temperature sensor, speed regulator and some key communication. Everything works, but among the three they have been repeated more than 400 times, all sporadics, and I think I remember that the upper column or something are produced. He is 4 years old and I do not know if the reviews have passed, now he has 34000 km. Do you know anything about the subject?
Greetings and thanks