PID Detector

Your car is a network of modules, each represented by an electronic control unit (ECU) with its own parameters. PID Detector first identifies which modules your car has. It then sweeps each ECU for every parameter it could have, up to 65,536 per module, and takes note of which ones answer in what's called an ECU map. This is known as a "brute force" approach.

Pelican's ECU map file format captures the modules a car responds to and the parameters each one answers to.

Knowing where to look doesn't tell you what the parameter means. To figure that out, you need to gather a large enough body of responses over time to start identifying patterns in the data that correlate with known values.

To do this, you can turn an ECU map into an OBDb signalset on your fork of your car's OBDb repo on GitHub. Point Pelican at your fork and every drive will start to record what each parameter answers, building up a dataset over time.

Once you have identified a pattern in the data, you can start to form theories about which parameters might mean specific values. Press the accelerator, turn the steering wheel, or watch the odometer climb, and look for the parameter whose values move with it.

Once you think you know what a parameter means, you can give it a name and units so that Pelican will interpret it as the value it represents. If you're fully confident in the value, you can even push it as a pull request to the OBDb so that every driver of that car benefits from your discovery.