2004 Nissan Quest - Shuts down

Good day, I bought a Nissan Quest 2004 3.5 SL for my father a month ago. He has called me twice this week that the engine shut down while driving on the highway. What really is the issue with it. Is it engine or electrical problem?

On a 16 year old vehicle could be multiple problems. If you want us to give you some ideas you need to post all the usual information.
Are you going to repair it yourself?
If not, then your father should take it to an independent mechanic.

It is going to take a shop to actually solve this . They will check codes and may charge a diagnostic fee.