OBD Express

API and GUI for communicating with On-board Diagnostics (OBD) Systems of modern automobiles.

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Welcome to OBD Express

This application provides a simple and intuitive GUI for reading diagnostic data, error codes, and other system information from you vehicle. My long-term goal is to also add the capability for interacting with some vehicle systems (resetting the trouble light, manufacturer specific features, etc.), providing a bus dump/scan feature for passively monitoring all bus transmissions, and providing a trip logging feature that works with GPS and Google Maps.

Architecture

This solution presently includes 6 individual projects:

  • ELM327API: This is the API for interfacing with an ELM327-like device, reading and processing diagnostics data from the OBD/bus, and transmitting any commands to the OBD/bus.
  • ObdExpress: The actual GUI interface that uses the ELM327API project to monitor the OBD/bus and display data.
  • BasicHandlers: Handlers that process OBD messages relating to the most commonly supported information on vehicles (includes various temperature readings, engine RPM, and VIN Number).
  • EngineDemandHandlers: Handlers that process OBD messages specifically related to engine demand (includes engine load, throttle position, pedal position, and torque).
  • DiagnosticHandlers: Handlers related to the vehicle's malfunction detection system (includes MIL lamp, ECU DTC counter, and others).
  • MiscHanlders: Handlers that process messages not normally used by normal users (includes handlers for messages related specifically to pollution control systems).

Modularity

OBD Express is designed to be a modular application. The application is structured so that it is a trivial task to add additional protocol support. Currently, OBD Express only supports 11-bit ID CAN messages. Support for 29-bit ID CAN messages will be added soon. I hope that other protocols will follow.

OBD Express has also made modularity a first-class consideration regarding OBD message support. Additional Message Handlers can be can be bundled as DLLs and added as plug-ins within the application.