What is the difference between OBD1 and OBD2?

[Rafael]

Here is the relevant introduction to the differences between OBD1 and OBD2: 1. Function: OBD stands for "On-Board Diagnostics." This system continuously monitors the engine's operating conditions to check if the vehicle's emissions exceed the standard. If they do, it will immediately issue a warning. When a fault occurs in the system, the malfunction indicator lamp or check engine warning light will illuminate, and the powertrain control module will store the fault information in memory. Through a specific procedure, the fault code can be read from the PCM. Based on the fault code, maintenance personnel can quickly and accurately determine the nature and location of the fault. 2. Difference: The difference between OBD-II and OBD1's on-board diagnostic system lies in its strict focus on emissions. Its essential function is to monitor vehicle emissions. When the emissions of carbon monoxide, hydrocarbons, nitrogen oxides, or fuel evaporation pollutants exceed the set standard, the malfunction indicator lamp will light up to alert the driver.

[Craig]

I've been fixing cars for decades, and the differences between OBD1 and OBD2 are significant. OBD1 was used from the 1980s to the early 1990s, with each manufacturer using their own protocols—like GM, Ford, and Toyota, whose interfaces and data codes were completely different. Fixing them required a bunch of specialized tools, which was a real headache. I remember one time a customer's check engine light came on, and after hours of troubleshooting, I realized it was Toyota's proprietary system with its confusingly coded diagnostics, making misdiagnosis easy. But since 1996, OBD2 became mandatory in the U.S., standardizing the 16-pin interface and protocols. Now, you can plug in an inexpensive scanner to read real-time data like engine RPM and emission values, and easily clear trouble codes. This saves me time and money, making repairs faster and more accurate. OBD2 also supports more sensors, helping detect emission exceedances, which is better for the environment. In short, times have changed, and when car owners upgrade, they should prioritize vehicles with OBD2 systems.