# OBD11 - can you leave it plugged in 24/7?



## amflemi (Jan 21, 2020)

Can you leave an OBD11 Bluetooth sender such as Carista plugged in all the time? I'd want to use it for real time monitoring of various things on a tablet. My old A4 used to throw an error light after a while which is why I'm asking.


----------



## SwissJetPilot (Apr 27, 2014)

I can't speak to the Carista, but for OBDeleven device, no, you can't leave it plugged in 24/7 without draining your battery. As soon as you plug in the OBDeleven dongle, the internal red LED light comes on, even with the ignition off, so that proves the OBD port is always live. Fortunately, the OBDeleven App has a built in alarm to remind you to remove the dongle once you've finished your scans.

However there are versions of the OBD-dongle that do have built in on-off switches as shown below -


----------



## ab54666 (Nov 18, 2019)

From Carista;

"The Carista device doesn't heat up (it has a low-power sleep mode), but we still don't recommend leaving it plugged into the car when you're not using it because you're potentially exposing your OBD port wirelessly to anyone walking by your car. Now, when the car is off, most of its computers are off too, so I don't know of any exploits of this that could do any harm to your car, but still, my recommendation is to plug in the device when you need it and unplug it when you're done and keep it in your glove box. As you know, it's really easy to plug and unplug - most Audis don't even have a cover on the OBD port."

It's so easy to install/take out just do that every time.

That said i'm having an alarm installed that when switched on disables the OBD port so potentially could leave it in.


----------



## John949 (Apr 12, 2017)

It does depend on te design o te sender as some may have the Bluetooth radio on permanently. Even so the current draw would be fairly small - on a par with the Alarm / Central locking systems - so if you use the car regularly, I don't think the drain would be a problem.

I'm not sure the security aspect is a problem either as not many (if any) of the ECUs will respond to diagnostic commands without the ignition being on. My suspicion is that the Gateway is turned off, if so there is no way to interfere with anything else.

If you wanted to be absolutely sure then change the wiring to the OBD port so that it receives it's feed from a switched 12V rather than a permanent 12V. I really don't know why Audi don't do this anyway. I'm sure most of my other cars powered the OBD port from a switched 12V.


----------



## Essex2Visuvesi (Oct 22, 2019)

John949 said:


> I really don't know why Audi don't do this anyway. I'm sure most of my other cars powered the OBD port from a switched 12V.


I can't think of any cars I've ever connected to that has the OBD port on a switched power feed


----------



## ab54666 (Nov 18, 2019)

Part of the EU regs I believe to have constant power.


----------



## amflemi (Jan 21, 2020)

Thanks All for the replies. I was looking at getting an OBDeleven so that might cover all the issues. I used to forget that the OBD11 was plugged in and only remember when I next went to the car. I am ashamed to say that I hadn't even thought about the security aspect. So that is a good call. I appreciate all the help.


----------



## ab54666 (Nov 18, 2019)

These aren't the most stolen cars and Mk2 isn't keyless entry or start which helps! That said I've seen two TTRS's and a tuned TTS stolen over the last month or so, so best to be as safe as you can but don't think it's really an issue..

A Pandora alarm cuts the OBD port when the car is alarmed, as I suspect other aftermarket alarms can do.


----------



## John949 (Apr 12, 2017)

> Part of the EU regs I believe to have constant power.


I did wonder as the cars I was thinking of had OBD2 sockets before it was mandatory. It does seem pretty silly to have a permanent 12V feed on the socket when none of the ECUs (or indeed the Gateway) will respond unless the ignition is on. Someone in Brussels must have thought it was a good idea.


----------



## kerwinrobertson (Sep 3, 2018)

You can use one of these 
https://www.amazon.co.uk/OBDLink-427201 ... 51&sr=8-35


----------



## andy mac (Jun 24, 2019)

You can buy extenders with a built in switch if you want to leave it plugged in all the time.
Makes it more accessible too.

https://www.amazon.co.uk/Autool-Extensi ... B074V59LY2

^ That one's showing as out of stock, but it's just an example, there are loads if you Google "OBD2 switched extender"


----------



## Taylortony (Feb 10, 2012)

kerwinrobertson said:


> You can use one of these
> https://www.amazon.co.uk/OBDLink-427201 ... 51&sr=8-35


Is that any good and what is the difference between it and the other similar one they do, I'm considering buying a reader for my TTS.


----------



## SwissJetPilot (Apr 27, 2014)

You could always splice into the OBD harness and add your own on/off switch for position 16. Simply put the OBD on/off switch in your ashtray or other inconspicuous location.

The secondary advantage of this is it would prevent an unauthorized OBD-dongle from getting power and prevent thieves from disabling your vehicle immobilizer or de-activating the alarm.

*3D Printed "Button Box" Ashtray Replacement*
https://www.ttforum.co.uk/forum/viewtop ... &t=1876249


----------



## kerwinrobertson (Sep 3, 2018)

Taylortony said:


> kerwinrobertson said:
> 
> 
> > You can use one of these
> ...


Its pretty good, works well with the Torque app.


----------



## John949 (Apr 12, 2017)

> The secondary advantage of this is it would prevent an unauthorized OBD-dongle from getting power and prevent thieves from disabling your vehicle immobilizer or de-activating the alarm.


There are cars where this can be done (MK1 TT for example) but I don't believe this is possible on the MK2 as the OBD port is only connected to the Gateway Module and thus you would have to 'persuade' the Gateway to forward messages to the Engine ECU using the CANID of the immobiliser. My understanding is that the Gateway is programmed not to allow this.

I did look into disabling the immobiliser or even reading the PIN code from the engine ECU (in order to program spare keys) and the general view is that the TFSI engine ECU is very hard to crack (That section of code is encrypted and protected from change - unlke the maps). My understanding is that the easier route is to spoof the immobiliser into thinking the correct key is present.


----------

