What is the function of an onboard diagnostic system (OBD)?

The function of an onboard diagnostic system (OBD) is to monitor vehicle performance and emissions while also storing trouble codes. This system continuously evaluates the performance of the vehicle’s engine and other critical components to ensure they are functioning within optimal parameters. When any component shows signs of malfunction or deviates from expected performance—particularly in terms of emissions— the OBD triggers a diagnostic trouble code (DTC). This code helps technicians diagnose issues more quickly by indicating which system may be experiencing a problem.

Monitoring emissions is particularly important, as many regulations are in place to control air pollution from vehicles. By tracking emissions-related components, the OBD helps ensure compliance with environmental standards. The data collected can also assist drivers in maintaining their vehicles by alerting them to problems before they worsen, ultimately enhancing the vehicle's overall efficiency and lifespan.