OBD Switch?

**eigenVector** · 04-21-2009, 10:31 PM

Not sure if there's a good place for this, but since it doesn't appear this particular forum has been used for anything, this must be the place!

So I've got a ELMScan 5 (the Bluetooth variety) from ScanTool.net, but I was looking for a way to leave it plugged in permanently. Is there anything on the market that works like a 'switch' to connect/disconnect the device when I turn the car off so that it doesn't drain the battery?

Thanks!

**Vitaliy** · 04-21-2009, 11:45 PM

On some cars, the OBD connector shares a fuse with the cigarette lighter, and turning off the ignition turns off power to both.

I'm not aware of any switches for OBD. You can just unplug the OBD cable, of course that's not a very elegant solution.

If you feel comfortable doing this, you can look into modifying your wiring to cut power to the DLC when ignition is off.

Vitaliy

**gsnathan** · 05-02-2009, 03:05 AM

I have the same issue with the Elmscan USB. Its power LED light remains on even when the car's engine is switched off. Am looking for some form of solution to either automatically turn off or a manual switch to turn off.

Didn't know that the Elmscan would draw power even when off. If I knew, I wouldn't have bought the unit. It's too much trouble.

**Vitaliy** · 05-02-2009, 11:20 PM

Originally Posted by gsnathan

I have the same issue with the Elmscan USB. Its power LED light remains on even when the car's engine is switched off. Am looking for some form of solution to either automatically turn off or a manual switch to turn off.

Didn't know that the Elmscan would draw power even when off. If I knew, I wouldn't have bought the unit. It's too much trouble.

Nathan,

I'm not aware of any currently available PC-based scan tools that have an automatic power shut-off feature.

Can you describe your setup in more detail? What prevents you from unplugging the OBD cable, when you leave the vehicle?

We've been considering designing in features that would make the scan tool more CarPC-friendly. Going to sleep is easy, waking up is the hard part.

Vitaliy

**critternz** · 06-08-2009, 05:03 AM

I have a Toyota Estima van and have found that with the Ignition off, the ELM scan power light stays on too.... this is due to the fact that the power supplied to the OBDii Van socket does not isolate with the key. It would be easy enough to 're-wire' that particular feed (16) into something that does isolate with the key

Critter

**teo** · 06-14-2009, 09:43 AM

Why dont you check how much power it consumes?

It could be that it consumes about the same amount as the clock inside the car. In that case i would not bother unplugging it.

Plus would it not be cool to connect to you car whenever you want and whenever it is in the garage?

Teoman

**Vitaliy** · 06-14-2009, 12:13 PM

Originally Posted by teo

Why dont you check how much power it consumes?

It could be that it consumes about the same amount as the clock inside the car. In that case i would not bother unplugging it.

Plus would it not be cool to connect to you car whenever you want and whenever it is in the garage?

Teoman

ElmScan 5 pulls around 75-100 mA. As long as you drive the car every day, this won't cause any problems, but if you plan to park the car for more than a couple of days, just unplug the OBD cable.

It is possible to drain the battery in just one night by leaving ElmScan 5 plugged in. Normally, when you turn off the ignition key, the ECU goes to sleep. If you keep sending messages to it, it will stay awake and pull several amps (because when the ECU is on, the actuators are on, too).

So make sure that (1) nothing is sending messages over the serial link and (2) have the software issue an ATZ command before exiting, so that the scan tool stops sending keep-alives.

Vitaliy

**eigenVector** · 06-14-2009, 01:03 PM

Originally Posted by Vitaliy

ElmScan 5 pulls around 75-100 mA. As long as you drive the car every day, this won't cause any problems, but if you plan to park the car for more than a couple of days, just unplug the OBD cable.

It is possible to drain the battery in just one night by leaving ElmScan 5 plugged in. Normally, when you turn off the ignition key, the ECU goes to sleep. If you keep sending messages to it, it will stay awake and pull several amps (because when the ECU is on, the actuators are on, too).

So make sure that (1) nothing is sending messages over the serial link and (2) have the software issue an ATZ command before exiting, so that the scan tool stops sending keep-alives.

Vitaliy

So I really shouldn't be worried about accidentally leaving it in for 24-36 hours when it's not being used? Great!
However since this is bluetooth, it is quite easy for a bluetooth hacker to recognize the device and start issuing commands to it to run down the battery. It's a low probability, but an important factor to consider. I guess that's also a worry anytime it's plugged in at all.

On another note:
As a fix for my problem, I found a way to mount my OBD cable in the rear of the cubby hole beneath my stereo. With this I can slide the ElmScan in and out of the socket now with very little effort. I had some cables run for my monitor when I asked the guys at the local stereo installation company I go to about it, and this is the solution they came up with. (Autogressive is the name of their business btw.)

Here's a picture of it when it's slid into place.

I'll see if I can take a better shot of how it's held into place later.

This works pefectly for me.

**nalav** · 06-14-2009, 10:38 PM

A possible solution would be to find which wire the power is coming from, and wire a switch or even relay to it controlled by fusion brain or something like that. That should ensure it's not drawing power unless you want it to.

**Vitaliy** · 06-15-2009, 12:22 AM

Originally Posted by eigenVector

So I really shouldn't be worried about accidentally leaving it in for 24-36 hours when it's not being used? Great!
However since this is bluetooth, it is quite easy for a bluetooth hacker to recognize the device and start issuing commands to it to run down the battery. It's a low probability, but an important factor to consider. I guess that's also a worry anytime it's plugged in at all.

On another note:
As a fix for my problem, I found a way to mount my OBD cable in the rear of the cubby hole beneath my stereo. With this I can slide the ElmScan in and out of the socket now with very little effort. I had some cables run for my monitor when I asked the guys at the local stereo installation company I go to about it, and this is the solution they came up with. (Autogressive is the name of their business btw.)

Here's a picture of it when it's slid into place.

I'll see if I can take a better shot of how it's held into place later.

This works pefectly for me.

Cool! Yes, security is a concern with Bluetooth, at the very least I would suggest changing the PIN.

What are the other things visible in the picture? Edit: nevermind, I see that it's a USB hub and the Blutooth dongle.

Vitaliy