OBD-I or OBD-II What's the Difference

OBD-I:

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.

OBD-II

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.

OBD II Data Link Connector | Apex Automotive

Photo of OBD II Data Link Connector

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