OBD-I or OBD-II What's the Difference
1. approximately 1980 - 1995 vehicles;
2. very basic computer;
3. no scanner necessary to download codes; rather, use jumper wire to ground terminal and count blinks of check engine light;
4. no standardized coding format;
5. no standardized data connector style or location;
6. had sensors to run basic aspects of the engine;
7. could turn on some emission controls like an EGR or Purge Valve;
8. could not test emissions components to verify if they were working as intended;
9. to test emissions components, exhaust gases must be sniffed from the tailpipe while tires roll on a dyno.
1. 1996 - current year models;
2. more advanced computers; requires scanner to download codes;
3. standardized diagnostic trouble code (DTC) format;
4. standardized data link connector (DLC) and standardized DLC location (within 2' of steering column, driver side or console;
5. had numerous sensors to run the engine, turn on emissions controls, and verify emissions control functions;
6. to test emissions, computer function must be verified by plugging into DLC, check engine light must not be illuminated.
Photo of an OBD-II Data Link Connector. Typically found under the driver side dash near the steering column.
Photo of OBD II Data Link Connector