So I've been through the same thing the engine runs the fan constant until the engine shuts of I've had the dpf cleaned the fan control module replaced and fan switches replaced nothing has sorted it but my local independent garage has been looking into the software's and discovered that there is a software setting that says engine cooling and gives the option single fan and twin and they are set to constant..the main dealership did not even know about this and just charges and a little garage workout it's in the software settings