15A DOME fuse keeps blowing; identifying J6

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by John McG., Dec 15, 2018.

  1. John McG.

    John McG. Junior Member

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    I've read a number of threads on this fuse blowing but no one seems to provide final resolutions. Unfortunately a common problem in forums. Toyota lists 32 different devices/subcircuits with power flow through this fuse. I'm not sure how that's a good thing especially for diagnostics. Looks like the power flow comes through a firewall harness into a junction connector J6 somewhere under the glove box. Is their an easy way to identify it? There is a lot of connectors under there. I also noted in the doc. that J6 is a "short connector". What is that? Looks likes its a connector where a lot of power is tapping off toother circuits. The example picture makes it look like its NOT a male/female connector but has contacts that complete the connection to multiple circuits. It looks like these contacts are individually removable. If so can they be removed and then put back one at a time to troubleshoot the many connections?

    Anyone have experience troubleshooting this circuit? Would I be so lucky that there is a common problem that tends to blow the DOME 15A fuse? Help is always appreciated.
     
  2. bisco

    bisco cookie crumbler

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    are you using tech stream and the service manual for trouble shooting?
     
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Any accident damage to the car that would have caused wiring harness damage? If so, that would be the first place to look.

    If you are not aware of any wiring harness damage, then I think you are on the right track by trying to identify the junction connector J6 to see if you can take that apart so that you can measure resistance to ground of one downstream circuit at a time.

    This is the sort of issue that seems minor but could end up with you towing the car to your local salvage yard. Good luck with your investigations and please let us know the outcome.
     
  4. edthefox5

    edthefox5 Senior Member

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  5. John McG.

    John McG. Junior Member

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    Ed, you really think so? It could have been the harness in the driver's door. It was damaged and replaced with a used door. A wee bit of sleuthing to do before pulling everything apart. Been there, done that and usually end up with more issues than when you started.

    I'll have to make up a load/test light then work for J6 back. Are these junction connnectors marked in anyway?

    John
     
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I doubt the inverter is the issue as the DOME fuse does not feed any circuit within that assembly. The inverter is powered down when the car is IG-OFF, while the DOME fuse provides power to some circuits continuously.
     
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  7. Elektroingenieur

    Elektroingenieur Senior Member

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    There might be a molded-in part number or manufacturer logo on the connector body, but it’s unlikely there is anything designating it as “J6.”
    The Electrical Wiring Diagram (more info), in the Connector List section, shows the connector’s shape and the number and arrangement of terminals. J6 is a twelve-position connector, arranged something like this:

    ------- = -----
    |A|A|A| | |B|B|
    |C|C|C|D|D|D|B|
    ---------------

    You can also review the System Circuit section, one system at a time, to see the colors of the wires that should be present. The terminals marked “B,” for example, all have red wires: one wire from the DOME fuse and two wires to the driver side junction block assembly: one to terminal 1A-30 (the ECUB terminal of the Body ECU) and one to terminal 1A-13. The Relay Locations section of the EWD has a Driver Side J/B Inner Circuit page, which shows that 1A-13 is connected to 1L-8, 1F-7, 1M-3, 1M-4, 1M-5, and 1O-5.
    It means some of the terminals are shorted together inside the connector, as an alternative to wire splices. In the diagram above, all the terminals marked “A” are connected together, all the terminals marked “B” are connected together, and so on, but “A” is not connected to “B,” “C,” or “D.” If you have access to the complete EWD (EM03Q0U), see the illustration on page 10 for an idea of the construction.
    I’m not sure it’s really so complicated: many of the systems listed in the Power Source chart for the DOME fuse are there only because of the combination meter, which receives power from the DOME fuse, among others.
    Yes, but it might be better to start elsewhere, since there are really only two branches from J6 on the DOME circuit. If you’ve already confirmed that the load side of the DOME fuse is shorted to ground (i.e., it’s not an intermittent problem or an overload), you might start by disconnecting J23 (in the center console), and then J33 (above the headlining), to isolate most of the interior lamps and switches. If the fault is still present then, check interior light I18, and then proceed to other branches of the circuit.
     
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  8. John McG.

    John McG. Junior Member

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    I have the Toyota diagnostic software and cable and the service manual. I do not have a subscription.
     
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  9. John McG.

    John McG. Junior Member

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    Thanks for taking the time to look at this. As I learn the nomenclature used in this manual I have figured out. The connections you mentioned are a smart way to approach it. I'll try that today.
     
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  10. John McG.

    John McG. Junior Member

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    Is it likely that it might be the audio?
     
  11. Elektroingenieur

    Elektroingenieur Senior Member

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    The Radio and Player (connector R3, terminal 4, or connector R6, terminal 1) is one of several ECUs that receives power from the DOME circuit, among others. I don’t have enough information to say how likely it is to be the source of the trouble.
     
  12. John McG.

    John McG. Junior Member

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    Well, after tracking things down somewhat it appears disconnecting the radio plugs ( three of them} the fuses have stopped blowing. Also seems this knocked out my climate controls through the MFD.All the other DOME circuits appear to now work including all the lighting and switches, VSC, etc. Anyone heard of the radio blowing out fuses?
     
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  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    No, I haven't heard of that, but its great that you were able to pin the issue down to the radio assembly. If you note the part number, you can probably buy a used unit on eBay inexpensively.
     
  14. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I haven't seen it in a Prius, but I have seen other cars whose stereos consistently blew their branch fuses... until somebody removed the jammed CD they were furiously trying to eject.
     
  15. Knightrider

    Knightrider Junior Member

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    Any updates on this?
    I am about to change the Radio to see if I have a bad unit causing all my dome/smart key issues
    I am thinking at J6 is my issue as well-
     
  16. John McG.

    John McG. Junior Member

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    Basically I removed the radio using a video instruction on Youtube.
    It's not an intuitive process, you need to remove most of the dash starting at the far drivers side. The process of removing the radio must have jarred a short somewhere in the wiring. I could not trace it, and when I reassembled, the think worked and stopped blowing fuses, and it's been working ever since. Take your time on the removal. Its tricky pulling the plastic pieces off. They use friction clips that are quite stiff. A little too much pressure and they break.
     
  17. Knightrider

    Knightrider Junior Member

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    Oh I’ve had it out
    I want to check for power at radio and such
     
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