No. Overall marks will be count to prepare merit list. there is no subject wise cut off for DTU or JEE Main.

Qualifying marks criteria for B. E./B. Tech at DTU :

-Candidates need to have secured at least 60% aggregate marks in Physics, Chemistry and Mathematics at Senior School Certificate Examination Level/XII.
-They also need to have passed English as a subject (Core or Elective) at Senior School Certificate Examination Level


You did not mention your category so i am assuming General category.

To get Mechanical branch under Delhi home state quota and general category, your rank should be under 15000 in JEE Main and marks should be between 170-80 marks.

You can check category and branch wise cut off of DTU, Delhi by below link:

DTU Cut Off

Good Luck.