Hello dear Citroen municipality, I have been having a problem with my 1.6 HDI Citroen C4 for a long time. When standing/waiting at the traffic light, exhaust gases enter the interior. The funny thing is that there is an error from time to time “Service”: Control speed defective. From this point on, so when the emergency program is running, no exhaust gases enter the interior. At the next restart, all errors are gone and exhaust gases arrive when standing in the interior. I don’t know which component in the emergency prog and why then no exhaust gases come into the interior. Thank you for your help.