Short, dated notes from the work on the car and the app, newest first.
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The logger records about 120 values while the car is moving and writes them into one plain CSV file. Nothing clever about the format on purpose: it opens in any spreadsheet, and a few lines of script are enough to plot whatever you want from it afterwards.
That is the groundwork for the next step on the list, a road-tested Android build.
The engine computer on this car has two ways to talk. Generic OBD-II goes out over the PCI bus, and the app reads it without trouble: rpm, speed, load, coolant temperature, fuel trims, oxygen sensors.
The deeper data, knock retard, misfire counters and the like, lives on a separate serial line that Chrysler called SCI. An ELM327 cannot speak SCI at all. So for now the engine side shows generic OBD-II, and the app says so rather than pretending otherwise.
The transmission is a happier story. Its 545RFE data does come over PCI, and the app reads gear, input and output shaft speeds, torque-converter clutch state, line pressure, selector position and temperatures.
The first job was to find out who is actually on the WJ’s PCI bus. On the reference car, a 2002 European-market WG, sixteen modules answered: engine, transmission, ABS, body computer, airbag, instrument cluster, overhead console, radio, CD changer, climate control, driver door, passenger door, rain sensor, memory seat, immobiliser and the alarm module.
Two cheap ELM327 adapters went into the test. One talks on this bus without complaint. The other does not, even though both say ELM327 on the label. That is why an adapter guide is on the list, right after a proper road test. It should be useful to anyone wiring up their own tool for this car, too.
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