I bought a cheap (sub $10) ELM 327 Bluetooth clone OBD-2 diagnostic adapter on a local "ebay-style" market where the seller specializes in car diagnostics and has several thousand positive reviews (read: I guess this seller would not provide anything really harmful). The adapter is labeled with an "ELM327 v1.4" sticker and the device identifies itself as an "ELM 327 v1.5" over serial. I know v1.5 does not officially exist in the original ELM.
The adapter was able to pair with a European 2006 Volvo XC90. I ran through a few free diagnostic apps (namely 5 of them: Torque free, OBD Car Doctor free, DashCommand, ScanMaster and OBD Auto Doctor) while some of the apps connected to the car successfully to show OBD info, some could not connect. I was using the diagnostics for about 30 minutes.
A few hours later, the car had problems with starting the engine - a kind of "engine error" light flashed on the dashboard, but the car computer (the text display) did not display any problem. The car did not start on the first attempt but it did on the fourth. There was also low fuel in the tank which could have caused the bad start but probably not the "engine error" light (this light then disappeared).
My question is simple - can there be harm caused to any car or its electronics in general by using the OBD-2 diagnostic port? I know one can also write messages to the CAN bus with it but I have no idea what consequences some bad writes can have.
The photo of the adapter:
I am asking on 2 levels:
Can harm be done via OBD in general (with any equipment/scanner etc.)?
Can harm be done with the ELM 327 clone device I used?
The reason for engine starting problems was low fuel. More fuel was tanked and now the car starts without problems again.