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OBD2 has power but reader is blank (screen is backlit)

Discussion in 'Prius v Main Forum' started by PriusV2012gen3, Oct 9, 2024.

  1. PriusV2012gen3

    PriusV2012gen3 New Member

    Joined:
    Oct 9, 2024
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    Location:
    Oregon
    Vehicle:
    2012 Prius v wagon
    Model:
    III
    As the title says, I can get power from the OBD2 reader but the screen comes up blank and I'm trying to get through DEQ. The following story is not totally linear, but it's close so please take that into account when reading. Please note the photo below of the OBD2 unit before disassembly, I made absolutely sure to note the positions of each of the pins.

    I've used a bluetooth elm327 and then about 6 months ago it stopped reading the ECU. It could get power but would not connect to read anything. Worth noting I left the ELM327 plugged in for a year roughly and in retrospect, wouldn't do that again.

    I tested pin 16 and it was showing 12 volts, no problem.

    At this point I disassembled my OBD2 wiring from the white female connector socket, resulting in all the wires below being unplugged. I did work to carefully ensure that the top row of wires stayed separate from the bottom row, thus assuring I did not mix any of them up, specifically the two grey wires.

    I purchased a more robust, yet still cheap OBD2 Scanner.
    I additionally purchased a new white female connector socket.

    MY SHORTLIVED FIX (worked just a few days ago)
    I manually plugged the pin of each colored wire directly into my newly purchased OBD2 scanner (not the old elm327 bluetooth). At this point, everything worked, my scanner was able to read the VIN and appeared fully operational. Once again, this was after I plugged in each of the 10 wires into the scanner one by one.

    Broken again
    Next I rebuilt the old OBD2 female connector, the new one had not arrived yet, but I was eager to test if the reader would work. This is where the problem returned. The OBD2 reader is backlit and you can see it light up when the car engine is running. Unfortunately it does not appear to "boot up" and show the VIN or scan options, it's merely back lit. I pulled of all 10 connectors and pushed the backside of them with a pin as was suggested a video I can't link because this is my first post, all of them seem to securely slot onto the ODB reader pins.

    Retrying my short lived fix
    I once again manually plugged in all 10 connectors to the working OBD2 reader, this time, same problem as when they were in the white female connector, the screen lights up but the reader doesn't work.

    It's not my OBD2 reader
    I tried it on a different vehicle and it works perfectly and I got it to work exactly once with my Prius.

    It's not the power pin 16
    The fuse is good, the power is good at 12 volts, I'm certain of that.

    I cant find the OBD2 wiring pin-out schematic, here's my mostly unfinished guess.

    1. Grey Wire
    2. Purple Wire
    3. Black Wire
    4. Beige Wire (Chassis Ground)
    5. Green Wire (Signal Ground)
    9. Light Blue Wire
    11. White Wire
    12. Grey Wire
    13. Blue Wire
    16. Light Green Wire (12 Volt Power)

    I'm left with a least 3 questions
    1. What is the function of wires 1, 2, 3, 9, 11, 12, and 13?
    2. What do I test next?
    3. Does anyone have a schematic to the 2012 v hatchback?
    Side note: My back is tweaked from working on this upside down in the car, I removed the seat so i could lay down and have slightly easier access. I am running out of troubleshooting mojo so now I'm here at the forum on a prayer, pls halp and thank you for reading!!!!

    PriusVGen3OBD2pinout.png
     
  2. rjparker

    rjparker Tu Humilde Sirviente

    Joined:
    Jun 6, 2008
    8,486
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    Location:
    Texas Hill Country
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    I have just one question - why?

    IMG_6378.jpeg
    Wired Pin Locations Front View
    IMG_6379.jpeg


    Top tip: The scanner should be powered anytime, not just when the engine is running.
     
    #2 rjparker, Oct 9, 2024
    Last edited: Oct 10, 2024
    Air_Boss likes this.
  3. Air_Boss

    Air_Boss Senior Member

    Joined:
    Jun 2, 2012
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    Location:
    New Yawk
    Vehicle:
    2012 Prius v wagon
    Model:
    Five
    Also meaning an unswitched OBD2 device left in the port will increase the parasitic draw on the 12V aux battery with predictable long-term implications.