I am an electronics enthusiast and I am helping a friend decipher a wiring harness diagram for his vehicle. He sent me the attached image to help him figure out what wire goes to where, but both he and I have the question on what do the filled vs non-filled circles indicate. Any help on this would be greatly appreciated.

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  • Welcome to Motor Vehicle Maintnenance & Repair! If you could give us the year/make/model/engine of the vehicle in question, we can probably help you a WHOLE bunch better. Also to know what exact part of the vehicle we're looking at here. Knowing these things we can usually pull up regular wiring diagrams and see exactly what you're talking about. Jul 30, 2021 at 17:43
  • Without more detail, those with “bk” etc are the colors of the wires going to that terminal, no legend means no wire.
    – Solar Mike
    Jul 30, 2021 at 18:09
  • blk = spare or unused ? Jul 30, 2021 at 18:30
  • @TonyStewartSunnyskyguyEE75 blk? Where? bk & dkbl though...
    – Solar Mike
    Jul 30, 2021 at 19:19
  • Blk dot is what i meant. Vs wht dot Jul 30, 2021 at 19:44

1 Answer 1


Wiring diagram legends are invaluable for detailed info. The best answer would be from factory service manuals. Sometimes someone posts them online in vehicle forums from either personal manuals, dealer techs, repair shops, etc. These would be hit or miss at best. Alternatives are buying service manuals, subscribing to Alldata.diy or Mitchell data for online access to factory service manuals. Some local libraries have free access to alldata.

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