MVS Volvo Forums contributor mercuric tells us about the link — no pun intended — between ELM327 Bluetooth devices, OBD-II, and DICE, Volvo’s advanced diagnostic system.
Almost all commonly available ELM327 bluetooth adapters use a Chinese clone of the ELM327 chip. The initial offering of the ELM327 from Elm was not protected; it’s firmware could be easily downloaded, so knockoffs quickly came about. They are much cheaper in quantity than the real ELM327. Finding an adapter with a real Elm Electronics chip is quite difficult, although I haven’t had trouble with the clone. Sometimes it will be reluctant to connect at first, but I suspect this has more to do with bluetooth than anything else.
DICE is a CAN-BUS interface that is used with VIDA for 1999+ cars. It will not work with Torque, Torque specifically talks to ELM327 — ELM327 uses a specific protocol that makes it easy on the application, preventing the client app (such as torque) from having to worry about any of the connection details or handling parity, etc. It uses an AT command set much like a modem; details in the PDF available from the elmelectronics.com link above.
Anyway, the app connected to the ELM327 and I was immediately checking the ECU for stored trouble codes (had none), and getting a bunch of raw signal data off the ECU. The free app is kind of clunky so I bough the $4.95 paid version which is much nicer. On my 96 850 it can display the following signals:
MAP (my NA has a map sensor which was news to me)
O2 sensor 1 voltage (needs to be replaced, very lazy switching rate)
O2 sensor 2 voltage
Transmission temp (I don’t trust this one since its a manual)
Instant MPG (much faster update rate than the Volvo trip computer)
Long term fuel trim
Short term fuel trim
All done in real time.