Powertrain relay bypass??

[TJBaker57]

Here is a curiosity. I saw this in the Upull yard on a 2005 Trailblazer EXT, 5.3 M engine.



This joins fuses #22 and #55 together. #22 is IGN E powered directly by ignition switch terminal C in RUN and START. #55 is the O2A fuse powered by the powertrain relay which in turn is controlled by the PCM.

I am wondering if they had a powertrain relay issue or were they bypassing a fault in the fuseblock base like a cracked solid copper wire/trace?

Also noted a battery to body ground wire that was only hand-tight and by the looks of the terminal eyelet at least appeared to have been not making any contact for some time.





I had thought about taking the ECM and TCM to add to my collection of test subjects but decided to leave them as someone may want that engine and related controllers.

 

[mrrsm]

THAT is being Very Thoughtful and Considerate, Thomas... Good Man!

This Oddball Wiring Side-Step is probably related to having a Bad Ignition Switch in combination with a Bad Brake Pedal Switch as per this TV Discussion lead by "The Roadie":

Ignition E Fuse (#22) Keeps Blowing

www.trailvoy.com

 

[TJBaker57]

Bad Ignition Switch in combination with a Bad Brake Pedal Switch as per this TV Discussion lead by "The Roadie":

Of the 3 circuits at the brake switch only one connects to the IGN E fuse and that circuit is closed until the brake pedal is pressed. Seems unlikely to me that could be related to this mystery.


What really interesed me is the possibility of using this wacky jumpering seen here to bypass a cracked fuse lock bus wire beneath. Perhaps in diagnostics.

If one suspects a cracked bus wire is causing an intermittent power loss to a given fuse use this manner of jumpering to add a parallel path to the problem area from a known spot elsewhere in the same power bus.

 

[TJBaker57]

So while at the Upull yard I took a fuseblock for experiments. I had never removed one before.

Not nearly as much of a task as I had envisioned. Made easier by use of an "L" shaped pick. That made releasing the hold-down tabs fairly easy.

I want to have a go at opening up the block to inspect and document the various bus wire traces within.

In particular I want to know if the schematics accurately depict the order of fuse arrangements on the bus. If so it would simplify this notion of augmenting the bus with the unusual sort of jumper seen in my first image in this discussion.