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ELM327 Bluetooth Dongles

Modification Details

No one has ever asked me directly but it's a question that appears weekly online.

Can I Use A Bluetooth ELM327 Dongle On My Smart?

This is 1 of many versions of the ELM327 OBD dongle. There are many like it but this one is mine.

Can you use it?
Yes you can.

Will it do what I want it to do?
It depends what you want it to do.


It will work to a limited degree. 5 possible problems.

1 - The OBD on the 450 and Roadster isn't like other cars. It has a separate data line for all of the controllers.
This means that this device will only connect to the ECU so you can't delete errors like airbag, ESP etc.

2 - The k-line protocol that the smart uses isn't very fast and bluetooth introduces extra lag. So if you plan to use
this bluetooth dongle to display engine data on a phone or tablet, don't expect immediate updates.
Fast updating this like revs or boost can take up to half a second to catch up, so not super accurate.

3 - There have been rare cases of people reporting their mileage increasing when they aren't using the car.
After extensive questioning, the common denominator is that they had all used a cheap Chinese ELM OBD dongle.

4 - Many models (if not all of them) connect to the switched and permanent live connections on the OBD.
So, when the car is turned off, there will still be a slight current draw from the device.

5 - This is the biggest issue and the reason for the majority of people buying one of these.
Error codes.

You are only getting generic error codes from this device. You can read my thoughts on generic error codes here.

Torque And Similar Apps

Chances are, you just want to get Torque, Dash Command or one of the miriad of copies,
throw it on an old phone and connect it to the ELM327. All so you can display figures and gauges.
Let me ask you this. Why are you doing that?

Most of the time it's so people can say "look what I did" to friends and people online that they are trying to impress for some reason. When pressed on it, they'll say that they want it to show car data. But do you really need that data?

Are you honestly going to get your phone out, put it in the cradle, unlock the phone and open the app?
Maybe for a few days.

But what about monitoring the coolant temperature on the MHD?

That's the only good reason I have heard but also dangerous for the previous reason.
After a week, you won't bother connecting the phone.


You have driven the car fine without the extra data so do you need it? Do you need the distraction?
Posting the symptoms on a FaceBook smart forum will yield better ideas than a ganaric error code ever will.
And that's taking into account the idiots who don't have a fucking clue but feel the need to chime in with their bullshit thoughts.

I Still Want One

OK, click the "shop now" in the image above. It's an affiliate link so I'll probably make like 10p.


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