Eyup.

I've bought a cheap Bluetooth OBDII adaptor ( m.ebay.co.uk/itm/111088326026 ) which works fine with my 2002 Fabia SDI and a phone running CyanogenMod 10.2 and Torque. Great.

Is there any way that one of these adaptors can be used to do anything unpleasant to my ECU, or do they just read sensors and clear error codes? If that's all they can do, I'm not bothered who connects, but if it can do any more, I'd worry about leaving it plugged in as the Bluetooth PIN is 1234, which anyone would guess.

Usually not, but if you have a PC with suitable program than some not so innocent settings can be changed.

I would not leave it connected also because it drains your battery.

 

Now you can get cheap BT OBD adapters with 0N/OFF switch, the price should be around 5 GBP. I have one and it works just fine. And I just push the button when I need it (hardly ever    ).

If your that worried,although i would'nt be put a switch on the earth wire on your eobd plug that you can switch off when you do not need it.

Cool, sounds sensible. It's just a toy for me, really, until I have something I actually want to diagnose so I probably just won't leave it plugged in, but could always fit a switch if I can be bothered. Ta.