What it reads, module by module
Every module that answered on the reference car, a 2002 European-market Grand Cherokee WG, and what the app does with each one today. Every claim here was checked on that car before it went on this page.
The network
How the app reaches the modules.
- Bus
- Chrysler PCI, the Grand Cherokee’s low-speed data bus. One wire shared by every module on it.
- Protocol
- SAE J1850 VPW, 10.4 kbit/s
- Modules found
- 16 on the reference car, all listed below
- Connection
- An ELM327 Bluetooth adapter in the 16-pin diagnostic socket, driven by the Android app. Only some ELM327 clones manage this bus.
- Engine data
- Generic OBD-II over PCI. The engine computer’s deeper data sits on a separate serial line, SCI, which an ELM327 cannot reach.
Module by module
Grouped the way the car is. The full list of values and tests is on its own page.
| Module | What the app does today |
|---|---|
| Engine | Live data via generic OBD-II, both banks. Stored fault codes. |
| Transmission | 545RFE live data, gear ratio and converter slip. Fault codes read and cleared. |
| Module | What the app does today |
|---|---|
| Airbag | Stored fault codes. The app sends this module nothing but read requests. |
| Immobiliser | Stored fault codes. |
| Alarm module | Answers identification requests. Nothing more confirmed yet. |
| Module | What the app does today |
|---|---|
| ABS | Each of the four wheel speeds, vehicle speed, brake switch. Stored fault codes. |
| Module | What the app does today |
|---|---|
| Body computer | Doors, hood, liftgate, lamp and wiper switches, seat belt, brake switch. Lamp, chime and wiper tests. Stored fault codes. |
| Instrument cluster | Self-test with needle sweep and lamps. Fault codes read and cleared. |
| Overhead console | Stored fault codes. |
| Rain sensor | Answers identification requests. Nothing more confirmed yet. |
| Module | What the app does today |
|---|---|
| Driver door | Every switch on the panel. Lock, window and mirror tests. |
| Passenger door | Every switch on the panel. Lock, window and mirror tests. |
| Memory seat | Position sensors and switch inputs. |
| Module | What the app does today |
|---|---|
| Climate control | Fault codes read and cleared. |
| Radio | Answers identification requests. Nothing more confirmed yet. |
| CD changer | Answers identification requests. Nothing more confirmed yet. |
Not yet
What the app cannot do today, and why.
Deeper engine data
Knock retard, misfire counters and the engine computer’s other deeper data travel on a separate serial line, Chrysler’s SCI, which an ELM327 cannot speak. Until a dedicated interface works, engine data stays generic OBD-II. More in the notes.
Other cars
Other model years and the standard (non-HO) 4.7 are expected to be close, but have not been tested. Only one car, a 2002 WG, has been.
Does your WJ answer differently?
Only one car has been tested. If yours has other modules, or an adapter behaves differently, write.