OBD Port Questions...

[USNA91]

So I purchased a WiFi adaptor for my OBD port, and in conjunction with DashCommand, it works like a charm.

Except for one little thing...

Is there some reason the OBD port has constant-power? It's a pain in the butt in that 1) it's just another drain on the battery, and 2) the OBD WiFi stays on, which drives my iPad nuts as it tries to decide between the rig and the home network...

I know that Pin 16 is the culprit. I also know that there are plug-and-play solutions to this that provide a switch, so this is not anywhere near insurmountable.

But I have to wonder if wiring that port so it's only hot when the vehicle on is an idea, or if just installing a switch is a better one?

What say ye?

 

[Superjet]

It's part of the spec for all vehicles with OBD2

Pin 16 Battery Voltage

 

[Lugboot]

Not sure if there are any inspections where you live, but tampering with the OBD port to change Pin 16 is a big no-no.

 

[BlackWorksInc]

Pin 16 will always have battery Voltage, it's a requirement in the OBDII specification to allow scantools to communicate with the vehicle via an integrated 12v source. I don't know if you recall OBD-1 systems, but often you had to clamp onto the battery or use the cigarette lighter plug to get power for the scantool.

As for tampering with the OBDII Plug... that falls under the whole "Tampering with federal emissions devices is prohibited... blah blah blah" deal, which many people in the automotive world choose to ignore... despite it being a federal offense.

 

[bartvonwolf]

Is there some reason the OBD port has constant-power?

Wait, so you are saying with OBDII on 5th gens, there is constant power to the port even with the vehicle shut off? I have a nice Scan Guage 2 which I may decide to mount in my new 2016 Trail. Are you saying it will remain on when the ignition is shut off? Sorry for the noob question.

Bart

 

[flyrv9]

Look at it this way. That pin 16 is always hot because it's on the battery bus. The OBD II connector was not designed for accessory or other uses. It was designed as a vehicle interface for troubleshooting and programming.

I have a 95 Nissan that is OBD I and it doesn't have a port. To read codes you have to read the LEDs on the side of the computer!

 

[USNA91]

Wait, so you are saying with OBDII on 5th gens, there is constant power to the port even with the vehicle shut off? I have a nice Scan Guage 2 which I may decide to mount in my new 2016 Trail. Are you saying it will remain on when the ignition is shut off? Sorry for the noob question.

Bart

I can't speak to the Scan Gauge in particular, but if you use the wifi unit I have, the answer to your question is YES.

As for violating federal standards, screw 'em.

 

[96r50]

Wait, so you are saying with OBDII on 5th gens, there is constant power to the port even with the vehicle shut off? I have a nice Scan Guage 2 which I may decide to mount in my new 2016 Trail. Are you saying it will remain on when the ignition is shut off? Sorry for the noob question.

Bart

No, the Scangauge senses when the RPMs are at zero and shuts off shortly thereafter.