OBDII bluetooth adaptor and battery drain

Del Lardo · 19 Feb 2013 at 15:54

Just got myself an OBDII adaptor to play around with and noticed that even with the ignition turned off the adaptor is still active. The car gets used every couple of days wondering if it OK to leave it plugged in or if I should disconnect it when not in use?

gumpy321 · 19 Feb 2013 at 17:16

Active in what way? Mine just glows red when the ignition is off, which I assume is standby mode.

I take it out every night anyway, just to make sure. But when I've left it in and forgot, the car has always started fine.

steve45 · 19 Feb 2013 at 17:22

I'm sure all it will be powering is an LED, i've left one in over night before and had no issue starting in the morning, couldnt really say what its like longterm though.

Tom_ed1987 · 19 Feb 2013 at 17:32

It will be of a similar drain to a car alarm i.e. negligible.

miniyazz · 19 Feb 2013 at 17:45

Bear in mind that in some cars it may be possible to code new keys using the OBD port while the engine is off. This may not include bluetooth ones of course.

Del Lardo · 20 Feb 2013 at 14:27

gumpy321 said:
Active in what way? Mine just glows red when the ignition is off, which I assume is standby mode.

I take it out every night anyway, just to make sure. But when I've left it in and forgot, the car has always started fine.

I could see a lit up LED, probably worth having a closer look but I wasn't too inclined to yesterday as it's right down in the footwell and I didn't fancy scrabbling around on a wet drive.

miniyazz said:
Bear in mind that in some cars it may be possible to code new keys using the OBD port while the engine is off. This may not include bluetooth ones of course.

Good point, security could be a bigger concern.

megakid · 20 Feb 2013 at 15:05

I think OBDII bluetooth dongles have to have a standby mode built into them as the way most of them work is by polling the OBD bus for data rather than simply listening. If they didn't have a standby mode, they would continue polling even when the engine was off. I imagine most, if not all, have a standby feature that somehow detects the engine is off.