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GM Fuse and Relay Centers
Posted to Technical Tips Forum on 1/8/2013 36 Replies

I thought the group might be interested in seeing how a typical Underhood Bussed Electrical Center is constructed.

This is a recent thread where the PCM would not turn on fuel pump due to poor contact at a relay terminal.

http://members.iatn.net/forums/read/msg.aspx?f=forum2&m=334646&fv=4&ar=3038&qv=0

And this one: Bitten by a Fusebox

http://members.iatn.net/forums/read/msg.aspx?f=forum2&m=221775&fv=4&ar=2006

bottom view-assembled, removed from connectors

top view of assembled fusebox

(This is a random picture of an assembled Envoy fusebox, I think from an 03, not an 06)

So your first step is identifying which terminals are loose. Then take a picture of the layout so you can get all the fuses and relays back correctly. Tap out the bolts and drill the rivets from the bottom side of the UBEC. Just drill enough so the rivets can be pushed through. Separate the top and bottom layers from the fusebox.

[2006 GMC Envoy SLT, BATT/Charging/Starting Photo]

[2006 GMC Envoy SLT, BATT/Charging/Starting Photo]

[2006 GMC Envoy SLT, BATT/Charging/Starting Photo]

[2006 GMC Envoy SLT, BATT/Charging/Starting Photo]

[2006 GMC Envoy SLT, BATT/Charging/Starting Photo]

[2006 GMC Envoy SLT, BATT/Charging/Starting Photo]

[2006 GMC Envoy SLT, BATT/Charging/Starting Photo]

G6 BCM with same style terminals

You'll notice the terminals go straight through the board, directly connecting the vehicle harness to a fuse or relay. The fuse side is easily damaged by probing with oversize tools. You can imagine how much grief a slightly loose fuse or relay can cause. Copper buss wires serve as internal jumpers. Also the copper buss wires are not soldered or crimped, they are mechanically "punched" into a slot at the side of each terminal, similar to a scotchlok or phone wiring. We usually don't take these apart or repair them, but the ones we've repaired work fine. When you're done, snap it back together, push rivets back in place and tap bolts through. Bolts will tighten to the connectors below UBEC and hold the whole mess together.

Robert from Florida

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