OBD has changed significantly over the years since its introduction in the 1980s. Originally, the system would notify the user that there was a problem using the MIL, but wouldn’t store any information as to the nature of the problem. As cars became more advanced, the number of sensors installed in vehicles expanded, as did the amount of information stored inside the system.
The evolution of OBD systems can be split into two distinct phases based on the type of system popular at the time. These are described in more detail below:
The first OBD systems were proprietary in nature, so they differed between manufacturers. Prior to 1990, the codes, systems and information gathered by each OBD system varied widely from manufacturer to manufacturer. While these systems proved useful, they were unnecessarily complex for technicians to work with — technicians had to purchase a new tool and cable for every vehicle make or had to invest in a scanner that had an array of adapter cables for multiple vehicle makes. Due to the proprietary nature of these systems, users were often forced to go to dealership technicians to diagnose issues.
The push to standardize OBD systems didn’t start until the California Air Resources Board mandated OBD capability in all cars in 1991. The board didn’t issue any standards for these OBDs, however, causing increased difficulties for vehicle manufacturers and users. When the OBD-II standard was implemented in 1994 in response to this need, all previous forms of OBDs were retroactively classified as OBD-I systems.
In 1994, the California Air Resources Board issued OBD-II as a set of standards for OBD systems for all vehicles sold in California. This mandate was officially implemented in the 1996 model year and has been in use ever since. The Society of Automotive Engineers and the International Standardization Organization, known as the SAE and ISO, respectively, also issued standards for how digital information should be exchanged between ECUs and a diagnostic scan tool. The EPA further expanded the use of OBD-II following the passage of the Clean Air Act — as of 2001, 33 states and local areas require regular vehicle inspections to ensure that they meet emission standards, and OBD-II systems are a key part of these inspections.
The OBD-II standards are characterized by several requirements, including the following:
- OBD-II Connector: Modern OBD systems use standardized DLCs called Type 2 Connectors. This allows technicians to use the same cable, a Type 2 Cable, to access the digital communications stored in the OBD system through a port. The location of this port is not standard, but it is usually located under the dashboard on the driver’s side of the vehicle.
- System Monitoring: The EPA requires that OBD systems monitor problems that affect vehicle emissions. Many systems look into other metrics that are not included in this scope as a way to make it easier to find and fix vehicle issues, but the minimum requirement is set.
With this set of standards in place, technicians can service a wider variety of vehicles quickly and easily without the need for manufacturer-specific tools.