I've been having an issue where none of my OBDII interfaces that power off of the port itself can connect to the ECU, They get power but cannot connect to the iso9141 protocol even though both should be able to do so. I do have a self-powered, super old OBDII diagnostic reader that does work. While this is helpful I'd like for my Sprint Drive and my Bluetooth adapter to work so I can use my phone rather than this old.
My Sprint Drive does register the voltage from the port at 11.4v and I'm wondering if this would be enough to cause a connection error? I'm thinking about hooking up a different 12v source; but I can't see any reason why there would be a problem; none of the other stuff hooked up on the same fuse or ground is having an issue that I can tell...so I'm thinking bad port or a wire short? The fuses are all fine. Has anyone run into anything like this before?

Edited September 27, 20214 yr by laegion

Here are the relevant pages from the service manual, hopefully someone more knowledgeable than myself can spot something I haven't...

maybe a pin is pushed back and it is intermittent? Maybe try pushing or slightly 'bending' the scanner's plug up or down.

In your other post you indicate you have no battery nor any inclination or opportunity to get power to it to unlock the shift lock button.  Does it have power now? 

What type of power does your powered OBD scanner have?

You're positive those scanners work on other vehicles? 

What fuses interrupt power to the OBD port?  Maybe there's a fuse that can depower the OBD port but not the ECU or your powered unit is somehow backfeeding the ECU?

21 minutes ago, idosubaru said:

In your other post you indicate you have no battery nor any inclination or opportunity to get power to it to unlock the shift lock button.  Does it have power now? 

What type of power does your powered OBD scanner have?

You're positive those scanners work on other vehicles? 

What fuses interrupt power to the OBD port?  Maybe there's a fuse that can depower the OBD port but not the ECU or your powered unit is somehow backfeeding the ECU?

That wasn't my post, I just replied to it.
My old OBDII scanner uses 4xAA for power

Yes, all 3 interface with my '95 Legacy with no issues. My Bluetooth unit is just the generic elm327.

I've checked the fuse.

If you look at the diagrams it shows the power to the OBDII port is shared as a back-up power for the ECU and feeds two circuits on the main relay. One circuit powers the O2 Sensors, the other powers a bunch of valves and sensors.
 

Hmm. No idea.

I’ve seen individual cheap scanners not want to access an ECU with no rhyme or reason. But it’s not usually Subarus and it doesn’t seem like that’s your issue if it’s multiple scanners and the same vehicle.