Unknown sensor (?) wire

[KVacek]

So the wire that had 12v on it was the one you grounded?

Yup. Anything connected to 12V at one side and not grounded, so with no current flow, will measure 12V at the ground side until it's grounded.

 

[Rocket Man]

Yup. Anything connected to 12V at one side and not grounded, so with no current flow, will measure 12V at the ground side until it's grounded.

Exactly. It’s an open circuit and with DC the current only flows one direction, some argue from positive to negative but some say it flows from negative to positive. It’s all theory still. An open ground will usually show positive voltage if the circuit is trying to operate because the meter is acting as a path to ground although a weak one.

 

[KVacek]

It does look like a bullet connector, but if it's a repair it's really old. Bought the vehicle in 2008 with 36K. I sure didn't do it.

Looks like I never posted the final fix here, but with another thread that I started later.

I bought AllData DIY and got a wiring diagram. Turns out this was the ground for ALL the coil packs. No idea why some GM genius wanted these to run to the bottom of the engine or attach to a ground point that's basically unreachable with the engine in the vehicle, but that's what it is.

I made a good repair to the failed crimp and grounded it to a ground point at the left front of the engine - don't remember the ground point number any more. Still working.

But wait - there's more. The vehicle had previously died with no warning while running down a gravel road 35 miles away 8 months earlier - in July 2021. I had nothing with me and no known service available nearby, so I opted to spend an additional 111 to have it towed to the best and most honest mechanic I know here in town. Turns out he and his partner had retired THAT VERY DAY and I got to deal with their employees who had just bought the shop. They sat on it a week, after which time it started, so they decided it needed plugs and wires and nailed me over $700 for the job. No phone calls, no notice, just late Friday "It's done here's the bill".

They lost a customer.