fault on renault master van?

Hi

I have a problem with the engine cutting out randomly. Some times it runs for 5 days without any problems, and then with no notice it cuts out and I have to wait until the next day and go back to it and it starts up again. I have had 3 diagnostic test on it and each time it comes up with 2 codes that no-one recognises. I have had the crank shaft sensor changed but it has again cut out today. Can anyone suggest where I can go from here???