The EML light came on in our E350 CDI - had the code read and it’s DPF. We’ve not been far in the car recently so we know why it’s got to this point - job change has meant hardly any long runs. Anyway our mechanic reset the code and told me to go for a long run. I gave it an energetic run but only for about 8 miles and the EML light came back on the next day. Question is if I take it on a long run now will it run the regen or will I need the code cleared before I do that?