Under the fuse block itself there are wires going to plug in harnesses not to the fuse block?

DOUGROCK

MEMBER
2001 GMC SIERRA
8.1L
V8
4WD
AUTOMATIC
100,000 MILES

Under the hood there is a fuse block box.

Under the fuse block itself there are wires going to plug in harnesses not to the fuse block.

What are these plugs in harnesses operating? There is one on the right bottom and one on the left bottom and one backside.

Again, these are not part of the fuse Block!

See video by A1 auto, guy shows mouse nest under the fuse block and you can see these connectors on the floor of this box. What do they go to?

Sunday, March 16th, 2025 AT 10:15 PM

1 Reply

STEVE W.

MECHANIC
14,046 POSTS

Those are inline harness connectors. When a vehicle is built, they use connectors to various extension harnesses, like the engine has its own harness, the dash has its own and many other items as well. That allows them to be somewhat modular and just plugged together. In this case I believe those are connectors 100, 102 and 152. Attached are the location and the connection plugs with what they include. There are multiple circuits and signals in each one. C100 for example looks like it carries the signals and control circuits for drivability related to cruise and engine feedback. 102 is related to traction control and ABS while 152 is EVAP and fuel tank harness.

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