Can the OBD-II port be wired so it shuts off when car not running? - Honda CRZ Forum: Honda CR-Z Hybrid Car Forums
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post #1 of 12 (permalink) Old 06-29-2018, 09:53 AM Thread Starter
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Can the OBD-II port be wired so it shuts off when car not running?

Fellow Drivers,
I'm trying to get a OBD-II / instrument display working. My current problem is that when the car and the android tablet shut off, the OBD-II transmitter goes into "deep sleep". The only way I've found to wake up the OBD-II transmitter is to unplug it, then plug it back in.
I'm wondering if there is a way to re-wire the fuse box so that the OBD-II port no longer gets power when the car is off.
I'm using an android tablet (v 5.0.2), and an OBDlink LX bluetooth transmitter.

Thanks much for any suggestions!
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post #2 of 12 (permalink) Old 06-29-2018, 10:49 AM
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Not so much rewire the fuse box, but rewiring the OBD port so that it draws power from a switched source instead of it's original wiring.
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post #3 of 12 (permalink) Old 06-29-2018, 11:17 AM Thread Starter
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Thank you for the response!

Could you please provide more details, or maybe point me to a thread on this subject. I've tried searching this forum, but no luck...

How would I go about rewiring the OBD port? I can find a switched source, but I don't know where the OBD port gets it's current power...
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post #4 of 12 (permalink) Old 06-29-2018, 11:25 AM
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Or you may be able to use male and female connectors( or modify an extension cable) and wire all connections straight through except power and put a manual switch on that so you are not permanently changing the OBD 2 port. This is so if where you are they use OBD 2 for inspection the car responds as expected when your Android is disconnected for inspection.
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Thank you for the response!

Could you please provide more details, or maybe point me to a thread on this subject. I've tried searching this forum, but no luck...

How would I go about rewiring the OBD port? I can find a switched source, but I don't know where the OBD port gets it's current power...

Last edited by Spdbump; 06-30-2018 at 07:16 AM. Reason: Spelling grammar additional info
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post #5 of 12 (permalink) Old 06-29-2018, 12:35 PM
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Yeah do what spd said. You can get an OBD port extension harness and modify that instead of the OEM harness.
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post #6 of 12 (permalink) Old 06-29-2018, 12:50 PM
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Originally Posted by Spdbump View Post
Or you may be able to use a male and female connectors and wire all connections straight through except power and put a manual switch on that so you are not permanently changing the OBD 2 port so if where you are they use it for inspection car tesponds as expected when your android is disconnected for inspection.
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Yeah do what spd said. You can get an OBD port extension harness and modify that instead of the OEM harness.
Yes, this sounds way better than what I said.

You could probably go a step further than the manual switch and use a switching relay tied to an On-in-run-only circuit so that the relay is open except in run - saves you having to switch the thing on and off, which I think OP would find just as annoying as unplugging the OBD scanner each time.
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post #7 of 12 (permalink) Old 06-29-2018, 06:26 PM
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All of that sounds good, but will you have a problem with the readings turning "off" when auto-stop engages? ???
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post #8 of 12 (permalink) Old 06-29-2018, 06:30 PM
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All of that sounds good, but will you have a problem with the readings turning "off" when auto-stop engages? ???

I mentioned this before but some devices ( in my case a Scan Gauge II) have a setting to lessen issues when car auto stops. As for a relay circuit it depends what other circuit you use as the trigger. This is another vote for the very simple manual switch.
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post #9 of 12 (permalink) Old 06-29-2018, 09:45 PM
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i wrote a response, lost it as i was previewing it...

anyways, in short, i have the same unit, OBDLink LX Bluetooth.

it does go into a low-power mode when the vehicle is off. however, it is always receiving power. you shouldn't have to unplug it and plug it back in.

i think the issue here is that you need to re-connect the unit from within the app you're using manually. I use the OBDLink android app (which will prompt to connect on app start up) but perhaps other software may not talk well with the OBDLink.

it's one extra step from being set and forget, but i don't always monitor my vehicle so it hasn't been a particular issue for me. though it would be nice if it would just find and reconnect like most bluetooth devices.

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post #10 of 12 (permalink) Old 06-30-2018, 02:59 PM Thread Starter
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Quote:
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i wrote a response, lost it as i was previewing it...

anyways, in short, i have the same unit, OBDLink LX Bluetooth.

it does go into a low-power mode when the vehicle is off. however, it is always receiving power. you shouldn't have to unplug it and plug it back in.

i think the issue here is that you need to re-connect the unit from within the app you're using manually. I use the OBDLink android app (which will prompt to connect on app start up) but perhaps other software may not talk well with the OBDLink.
Thank you for the info and thoughts! I have been using Torque Pro on an android. I'll give other apps a try...
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