Battery Wiring / Main Engine Harness

Hello all,
I have a dead 06 Tundra DC SR5. 140k 4x4

Looking for a diagram or some knowledge on where to start with a "bad" main engine harness and snipped battery wiring. I'll explain

Driving. Check engine light comes on (secondary air stuck). I bring my truck into Toyota to look at this, and a parasitic draw I've had. (Also, radio cut in and out sometimes).

An $800 bill and a non-running truck is what I walked away with (long frustrating story). They said main engine harness. After Toyota, lights would turn on but shut off when the key was turned, didn't turn over. I don't think the starter clicked.
Quoted: Parts = $4,000 / Labor = $3,500

I bought a used harness and it sits right now.
They couldn't tell me what part of the harness was faulty. Just a bad harness..?

*The previous owner had some janky terminal hardware to accommodate a kill switch into the cab to help with that parasitic draw. So, I snipped off the ends of everything connected to the battery and pulled out the kill switch. Right now, it sits with a potentially faulty harness, and cut battery terminals, hardware saved. If I have to replace, I want to while I'm in there for secondary air light. (Harness Pictured) Thanks for the help!

 

Parasitic draw in interesting. Only because sometimes things will short out/ground inside the connectors due to corrosion depending where you live.

Secondary air valve being stuck is tied to SAIP system, which you can either bypass or repair, spendy as it is.

And on the harness, I mean, I don't see how it would be the issue but I'd expect the stealership guys to be correct. You could try swapping in the spare, assuming it's from an '06 with the same engine/tranny/drivetrain combo. If you want to get started on tracing what you have, there's some electrical diagrams linked in the 4th or 5th paragraph of this catch-all info thread: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

 

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Thank you - I have a feeling it is corrosion somewhere. I am in the PNW, and bought the truck real cheap, but it was once in NY.

At this point, I'm thinking the dealership just wanted it out of their hands, based on the full story. Maybe I just need to go find another DC and look at its wiring to compare.

The secondary air injection, I have the parts, and am looking to replace it, along with the water pump, fan clutch, timing belt, etc. - so I don't want to tear everything out twice. Thanks again!