Dupont jump wire in order to replace 20 pin cable
As said by brhans, the Dupont cable is most likely going to fall out due to the vibrations made by a car. One thing you could use to mitigate this problem is to install a proper cable connector. One of these could work: Connector

If you're not willing to use a proper cable connector though, you could always hot glue the Dupont connectors to wherever they need to go. This can give you some protection from vibrations but may not be the best solution.