CAN bus
Read your car's CAN bus, without sending anything
OBD Log listens to the data the car's modules already exchange and decodes it with definitions created and published by users themselves.
How it works
How CAN reading works
Three stages, from the car's wire to the value on screen.
The app listens
Through the OBD2 adapter, the app only hears the frames already travelling on the car's CAN bus, at 500 or 250 kbit/s, with 11- or 29-bit IDs. Reading only happens if the adapter delivers this data to OBD Log.
The definition decodes
A signal definition says, for each signal, which frame it is in, its size, factor, offset and unit.
The signal becomes data
Each signal enters the trip like any other reading: it shows in the app, in the history, in the video and to the AI.
Community
Definitions made by people who own the car
We do not maintain the catalog: each definition is published by a user and marked as community-made.
- Whoever owns the car publishes the definition, in JSON or DBC.
- Search by make, model, ECU and year.
- Public for everyone, or private by invite code.
- Versions never change: you update only if you want to. Nothing updates by itself.
- A wrong definition can be reported.
Artificial intelligence
AI helps decode
For the car nobody has mapped yet, the AI looks for the signals in the raw data.
See the AI page- With no definition in use, the app keeps the trip's raw frames.
- The AI summarizes what went through the bus and looks for the bytes that follow GPS speed or another value.
- It proposes the decoding and saves it as a private definition.
- You check it, install it and decide whether to publish.
Safety
Safe by design
A definition is read-only data. The format has no way to send a command to the car.
- No frame is sent to the car: the app only listens.
- A definition accepts no script, free formula or unknown field.
- Text containing a chassis number (VIN) is rejected.
- The worst that can happen is a wrong value on screen, never an action on the vehicle.
- Raw frames stay in your account and are deleted along with the trip.
Being tested
What is still missing
The OBD Log Core, in development, will have a second CAN whose passive listening is guaranteed by the hardware itself.
See the Core page- Validated with a simulated adapter; more cars and adapters still need testing.
- Only 500 and 250 kbit/s through the OBD2 adapter. Other speeds need a dedicated CAN adapter.
- Some adapters ignore silent mode: passive listening is only guaranteed on a reference adapter.
- Raw frames take up a lot: tens of MB per hour on a busy bus.
Find out what your car is saying
OBD Log is in Beta. Download the app and try it before everyone else.