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On-Board Diagnostics (OBD-II) Design Information

OBD-II is used by scan tool or other hardware to communicate with a vehicle’s on-board computer through an OBD-II connector located under the dash. The information contained here provides information related to designing custom hardware and software to communicate with any OBD-II equipped vehicles, such as:

  1. OBD-II automotive standards
    1. Protocols
    2. Enhanced OBD-II (manufacturer specific)
    3. PIDs (Parameter IDs)
    4. Diagnostic Trouble Codes (DTC)
  2. Software design
    1. Software implementation
    2. Protocol implementation
    3. Legacy OBD-II protocols
    4. Architecture
  3. Hardware design
    1. Schematics
    2. Microprocessors
    3. Protocols

About OBD-II

On-Board Diagnostics (OBD) II is a group of automotive diagnostic protocol standards used by a scan tool. OBD-II was mandated on most gas powered vehicles in 1996. The 16-pin OBD-II connector used to connect the scan tool is located inside the vehicle typically under the driver’s side dashboard. 

European on-board diagnostics (EOBD) is essentially the same as the US-based OBD-II and was mandated in 2000 for gas powered vehicles and 2003 for diesel powered vehicles. 

JOBD is OBD-II for vehicles sold in Japan. 

A scan tool communicates with one or more vehicle computers to send and retrieve diagnostic data. The diagnostic data varies widely depending on the vehicle make, model and year. In general, newer vehicles provide more diagnostic data. 

Common features on OBD II equipped vehicles include:

  1. Read diagnostics trouble codes
  2. Clear diagnostic trouble codes (DTCs)
  3. Turn off the check engine light
  4. Read live real-time sensor data
  5. Command on-board self-diagnostic tests (bi-directional commands)
  6. Read readiness monitors

Wikipedia provides an in-depth history of on-board diagnostics.

Auterra OBD-II OEM License

Do you have a product idea that requires communication using a vehicle's OBD-II diagnostic port? Need software source code and hardware schematics to get your project jumpstarted? If so, see the link below.

OBD-II Adapter Software Source Code

OBD-II Adapter Design

Auterra OBD II Scan Tools, Performance Meters and Data Loggers

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