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2015 Chevrolet Silverado
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Discussion Starter · #1 · (Edited)
Tracing down some electrical gremlins. RR brake light, power door locks, dome lights and center-console cigarette lighter have no power.

Found a low-voltage condition to the BCM. X5 pin 4 (Red/Yellow) is supposed to be B+, but I measured only 2 volts. When I supply it with +12v everything suddenly works.

So now I'm trying to trace that back to the source. I pulled fuse F45DR and I'm reading the same 2v on the hot side. Hot side is supplied by the X1 connector pin 21 (RED/LT GREEN), which measures that same 2v.

And now I start wandering in the woods. I'm not exactly sure where the other end of that RED/LT GREEN wire gets its +12v. I assume it's either the X2-G5 or X4-H5 from the under-hood fuse box, only because those two list Battery voltage and they're both Red/Lt-Green. BUT, both of those are 16-18 gauge wires. The RED/LT GREEN wire feeding the right panel fuse box is a thicker 10-12 gauge wire.

It'd be REAL nice if I could find an actual schematic FOR THE FUSE BOXES THEMSELVES. Every schematic I've pulled up so far on ALLDATA just ends at X51R interior panel Right with the universal "Magic Box* dotted line around it.

Anyone have any clues?
 

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Tracing down some electrical gremlins. RR brake light, power door locks, dome lights and center-console cigarette lighter have no power.

Found a low-voltage condition to the BCM. X5 pin 4 (Red/Yellow) is supposed to be B+, but I measured only 2 volts. When I supply it with +12v everything suddenly works.

So now I'm trying to trace that back to the source. I pulled fuse F45DR and I'm reading the same 2v on the hot side. Hot side is supplied by the X1 connector pin 21 (RED/LT GREEN), which measures that same 2v.

And now I start wandering in the woods. I'm not exactly sure where the other end of that RED/LT GREEN wire gets its +12v. I assume it's either the X2-G5 or X4-H5 from the under-hood fuse box, only because those two list Battery voltage and they're both Red/Lt-Green. BUT, both of those are 16-18 gauge wires. The RED/LT GREEN wire feeding the right panel fuse box is a thicker 10-12 gauge wire.

It'd be REAL nice if I could find an actual schematic FOR THE FUSE BOXES THEMSELVES. Every schematic I've pulled up so far on ALLDATA just ends at X51R interior panel Right with the universal "Magic Box* dotted line around it.

Anyone have any clues?


This it?


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2015 Chevrolet Silverado
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12 Posts
Discussion Starter · #5 ·
Just for experimentation, I removed the under-hood fuse box and flipped it over (essentially removing every circuit in it from the equation) then hooked the battery back up. The connector that supplies the right-side fuse box still has +12, except, of course, for the RED/LT-GREEN which is on supplying +2.

This proves pretty conclusively that the under-hood fuse box has nothing to do with the problem.

So, again, where does that big RED/LT-GREEN wire get it's power??
 

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2015 Chevrolet Silverado
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12 Posts
Discussion Starter · #9 ·
And just to put this issue to bed, the issue causing all the problems was that the last 60A fuse on that B+ bus is flakey. And in classic Chevy style, you have to buy the whole assembly, $60, instead of just the metal bus strip with the fuses. :rolleyes:
 
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