OBD OBD1 and OBD2 are all the different electronics on different generations of motors. For example, most 88-91 civics are OBD and 90-93 Accords OBD1, then 5th gens and up are mostly all OBD2. If you are doing a motor swap and the new motor is a different OBD then you have to convert the electronics on the wiring harness, distributor, injectors, and wiring at the ECU.