I have build an OBD II (CAN) circuit that I am trying to integrate with a particle electron. The OBD II circuit works fine with a Terminal. I can not figure out how to use the serial communication of the electron (TX,RX). Any suggestion will be greatly appreciated.
I think you should check the thread for Carloop, the open-source product Particle and OBD-II ports.
OBD-II is CAN bus, which is similar to serial but is multi-drop and requires a transmitter enable and differential signaling. Details of how Carloop does this are in their github repo which you can find in that thread.