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I have connected a OBD2 adapter (Bluetooth ELM327) to my 2010 Mazda Axela (1990cc) and I've noticed that when my phone is connected to the adapter, the Mazda RVM alert lights on the side mirrors come on. (There was no other vehicles or obstacles around and the vehicle was stationary.)

When the phone is disconnected or the adapter is disconnected from the car, they go off after a few seconds.

Is this normal and expected?

I heard certain chinese knockoffs of ELM327 adapters can cause electrical issues with vehicles. So I want to know if it is safe to use the adapter with the car regularly for diagnostics and other things like dashboards on the phone .etc. using OBD2 data.

  • It is safe. Most likely this is just an undocumented function the car uses to show that it is talking to a diagnostic tool. I;ve seen something similar on an old Audi, when initiating communication with the ABS controller the related LEDs light up on the dash. – André Borie Aug 1 '16 at 19:49
  • but this stays on. Until I disconnect. Is there any way to confirm it is expected behavior? (and hopefully turn it off. I don't want the RVM warning light on all the time.) – Madushan Aug 2 '16 at 1:19
  • I think an ELM327 always maintains a diagnostic session with the vehicle until it is powered off or told to turn off (which your phone app may not do). In any case, don't worry about it - the data lines used by OBD2 are separate from the critical parts of your car - even if you short them together nothing bad will happen. – André Borie Aug 2 '16 at 2:13

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