Automobiles have various electronic systems inside them to manage infotainment, motion management, energy efficiency, emission norms etc. These electronic systems are called ECU Electronic Control Unit. The Firmware in these ECUs' needs to be updated at certain intervals and in case of any fault they need to be diagnosed as well. This requires a communication interface with outside world. It is achieved by means of Serial interface with the diagnostic tools/PC/data logger. The Existing Standardized connector provides a slow communication interface. Software updation in a modern car via this interface requires long time, which significantly increases the repair time, human efforts required to service a single car and subsequently the costs. Every time diagnostic software is developed the testing required to be done on real vehicle making the sophisticated systems inside car prone to be harmed by erratic behavior of On Board Diagnostics OBD program. This paper aims at presenting a fast and economical Ethernet communication interface in automotive applications by introducing a microcontroller as an intermediary between the serial Interface presented by ECU and the interface to connect to outer world (Ethernet), and a way to test the diagnostics program without the need of going to car each time. This will allow one to test the diagnostics program without affecting the ECU. Allowing one to utilize all the advantages presented by an Ethernet interface-easy interface with laptops/pc for software updation high data speed, implementing an Ethernet interface will allow the automobile to connect to World Wide Web creating endless possibilities. For instance remote diagnostics and software updation no need for car to be taken to service center; it could be done with the car in owner's parking! © Research India Publications.