Try an OBD-II MCP server without a car

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Run a real MCP client against a simulated vehicle. The companion obd2-mcp server includes a demo that prints tool responses. You need Git, Node.js and npm; no car, ELM327 adapter or AI subscription is required.

Automotive AI Skills supplies prompt frameworks. obd2-mcp supplies data-reading tools. This demo exercises the tools; it does not generate an AI diagnosis.

Run the demo

Use Node.js 22 or 24, the versions covered by the linked CI run. Build from source with these commands:

git clone https://github.com/shoka-jp/obd2-mcp.git
cd obd2-mcp
npm ci
npm run build
node examples/mock-demo.mjs

The script explicitly selects mock mode, reads four tools and closes the connection. It does not clear trouble codes. If you already have a checkout, update it before running the commands.

What output should I see?

The following fields were captured on 2026-10-29, using Node.js 24.22.1 on Linux. They are actual program output from simulated data, not measurements from a real vehicle. The script prints the full responses; this table selects the relevant fields.

MCP tool	Selected response
`connection_status`	`connected: true`, `simulated: true`, mock ELM327 adapter
`read_dtcs`	Stored code `P0420`, no pending codes, malfunction indicator on
`read_freeze_frame`	`98 km/h`, `2210 rpm`, coolant `88 °C`
`read_live_data`	`0 km/h`, `740 rpm`, coolant `89 °C`

Freeze frame records conditions when a fault was stored. Live data describes the current state. The difference is useful evidence to investigate; neither a code nor these readings alone proves which part failed.

Evidence and limits

Demo source and recorded results identify the implementation used for this guide.
Successful Node.js 22 and 24 CI run covers mock smoke tests and installation of the generated npm tarball.
The run does not establish real adapter compatibility, real-car diagnosis accuracy or behavior inside a particular AI application’s UI.
The worked conversations are separate teaching scenarios, not results produced by this program.

If the demo fails

Run node --version and npm --version and confirm you are in the cloned obd2-mcp folder.
If dist/index.js is missing, complete npm ci and npm run build first.
If an install or build fails, keep the first error and your OS and Node.js version. Report a reproducible issue, removing credentials and vehicle identifiers.

Use the data with an assistant

Read the MCP client setup guide. Once a client is connected in mock mode, combine it with the OBD-II Diagnostic Assistant:

Read the mock vehicle’s codes, freeze frame and live data. Separate observations from hypotheses and list what still needs verification. Do not clear codes.

For real work, follow the safety and verification limits.

Help improve the projects

Follow Sho on GitHub for project updates, contribute a correction, or sponsor the open-source work.