OBD-I, or On-Board Diagnostics I, is an early vehicle diagnostic system introduced in the 1980s. It was designed to monitor the performance of the engine and other essential systems, helping to identify issues that could affect emissions. OBD-I systems provided basic trouble codes that mechanics could read using a scan tool, allowing for easier troubleshooting. Unlike its successor, OBD-II, which offers more advanced features and standardized protocols, OBD-I systems varied by manufacturer. This lack of uniformity made it more challenging for technicians to diagnose problems across different vehicle brands. Overall, OBD-I laid the groundwork for modern vehicle diagnostics.