i need help with c++ program, if either the airbag is triggered or the deceleration detected is greater than 5 Gs, we consider that an accident occurred. The vehicle decides to ask nearby by sendig SMS.
This will be specific to each vehicle Manufacturer and some specific to make and model. It's not covered in OBD-II and is propitiatory for each manufacturer. You might be able to detect by monitoring the CAN buss but again it will be specific to each manufacturer. You may be better off using your own G-force sensor to determine if there has been an accident, although you want the threshold to be much lower than 5 G's. The sensor type varies but all but rollover sensors measure G-force, and require two separate sensors to close at the same time, sometimes called an arming and discriminating sensor.