The study of sensor failure and its effect on emission standard on petrol and diesel engine using five gas analyzer and KTS 570 is presented in this article. The sensor failure is checked with the help of ESI[Tronic] a software-based application helps to scan the whole sensor data of vehicle. The gas analyzer used has an ability to scan about five gases namely CO, CO2, HC NOX, O2 these are the main gases that can be easily scanned by analyzer. Along with those emissions standard ESI[Tronic] data were parallel monitored for the uniformity of engine running. This work presents the comparative study of BS III and BS IV engine behavior on sensor failure. The emission data were plotted and compared with each other for three different make.