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My ODB-II (ELM327) device has the default PIN of 1234. Is it possible to change this PIN? And how?

  • Welcome to Motor Vehicle Maintenance & Repair! I believe these are hard coded into the Bluetooth reader (ELM327). The one I have is set to 1234 as well. Realistically, though, does it really matter? If you're not using it, unplug it from the vehicle and nothing will happen to anything. – Pᴀᴜʟsᴛᴇʀ2 Dec 10 '17 at 21:06
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    I want to use it as daily use, and I don't want that someone else could easily connect. – juanmah Dec 10 '17 at 21:18
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    Someone has to know you're using it in order to know to connect to it (security through obfuscation). Next, they'd have to be in close proximity to your device in order to connect. I don't know the exact range, and it could depend on the device itself, but it's going to be limited. The other thing is, what would they be able to do to your vehicle through it? The worst would be to reset any codes. I guess if someone was truly nefarious, they could figure out a way to do something, but really, that's going to be minimal through an ELM327 device. – Pᴀᴜʟsᴛᴇʀ2 Dec 10 '17 at 21:34
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    As an information security consultant I understand your concern, 1234 is a well known default bluetooth password and people do scan for these things, sad as it is. From a risk perspective car computer security is swiss cheese, so I'd make sure that dongle is disabled when the ignition is off. – GdD Dec 11 '17 at 8:49
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Make cable to the device with an on/off switch in the +12v line - if it does not get power it won’t work - just remember to turn it off when you finish .

You could also use an ignition controlled relay to do the same so it comes on with the engine but will be off when you stop.

  • Don't they draw power from the OBD II port? – Steve Matthews Nov 27 '18 at 12:00

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