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Scantool still powered when truck off

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  • Scantool still powered when truck off

    When I turn my truck off, my Elmscan PWM scantool still shows power on the bus. It's been like this since I first got it last year, and it doesn't seem to pull much power, but I'd still like it to turn off when I turn off the truck, or even just turn off the computer.

    I tried searching for the pinouts on the OBDII interface (without much luck) to maybe cross the + supply wire over to an ignition wire, or even an output supply from my opus.

    Anyone know which wire on the OBDII connector is the main power, and what voltage that would be? ( shows the Elmscan PWM scantool at 12V operating voltage, but I want to be sure).
    My truck is a Ford btw, which would be PWM.

    99 Ford Ranger - Bagged and laying frame

    Current Carputer project:
    Custom mounted 7" LCD w/ TSK in radio bezel
    Custom center console for relocated headunit
    Via Epia M10000

  • #2
    The obd2 port will have a wire that shows you 12V. It (should) be the only one. Most vehicles this is an ignition-switched source, but if yours is constant power, I would just change it. Like you said, just give it power from your opus.

    edit: I would modify the scantool side of the connection rather than the car side, because if the plug is meant to have power all the time, maybe there are some tests the dealership runs where they need to have the ignition turned off. Other than that, I see no reason for it.



    • #3
      The OBD-II / J1962 Connector Vehicle End View

      Table 1 - OBD-II Pins and their corresponding neoVI signal

      J1962 Pin J1962 Pin Description
      1 Discretionary* (GMLAN SW CAN Line) SW CAN 1
      2 + line of SAE J1850 J1850 VPW or J1850 PWM H 2 or 6
      3 Discretionary* (GMLAN MS CAN H) MS CAN H 16
      4 Chassis Ground
      5 Signal Ground PWR GND 13
      6 Discretionary* (GMLAN HS CAN H) HS CAN H 14
      7 K Line of ISO 9141-2 ISO K 8
      8 Discretionary*
      9 Discretionary* (GM ALDL)
      10 - line of SAE J1850 J1850 PWM L 5
      11 Discretionary* (GMLAN MS CAN L) MS CAN L 17
      12 Discretionary*
      13 Discretionary*
      14 Discretionary* (GMLAN HS CAN L) HS CAN L 15
      15 L line of ISO 9141-2 ISO L 7
      16 Un-switched Vehicle Battery Positive VBATT 25

      * Discretionary means that the J1979 specification leaves this pin for use by the manufacturer.
      Attached Files
      Hack your car's CAN BUS at