Why is the wire designed like this?

[catimann]

During a repair the wiring that comes down through the trunk and goes to the diff and other places got a little burnt.

I noted some of the wires have a different sheath than I have seen before on cars. In this case a black rubberish/vinyl sheaths some aluminum foil as a sheath within a sheath. Then there is a bare silver wire (not copper) and a copper wire that is itself sheathed in a light green.
IMG_4275.jpgIMG_4281.jpg
So what is the purpose for this design? How important is the foil? Considering the foil is in direct contact to the silver wire it can't be a ground or for an electric purpose.

Ideas

[Randy Forbes]

Shielded pair, or sometimes coaxial (like your "cable" tv); that's probably the wiring for your wheel speed sensor(s).

Low voltage signal wires (1-5 VDC) is susceptible to outside electrical noise, and the shield keeps the signal clean.

Okay, that's layman's terms (with 3-decades of career instrumentation and electrical control work behind it) but I AM SURE that there are EEs on here that can give you the formal definition...

[CB750]

Randy, your explanation is right on target for this venue.
(IEEE Senior Member with 30+ years of radio frequency electronic engineering expertise)

[Randy Forbes]

Randy, your explanation is right on target for this venue.
(IEEE Senior Member with 30+ years of radio frequency electronic engineering expertise)

Gee, sometimes I surprise myself__I just know I've forgotten more than I remember

[CB750]

I just know I've forgotten more than I remember

Yeah, these days the older I get, the better I was...(laughing)

[catimann]

Ok thanks. So to repair this mess I attempted to reconstruct it as best I could laying under a car and only having two hands. The creator messed up there, just sayin.
I got as much of the foil exposed as possible and put two full wraps of Al. foil around it. Made it as snug fitting as possible and then black tape over the top of all of that.

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[CB750]

As long as your foil wrap has good connectivity to that bare silver wire you'll be fine; the bare wire should be connected to chassis ground.
Any energy that hits the foil shield is sent to ground via that wire, rather than interacting with the desired signal running on the internal conductor.
Using a multimeter on a low Ohms setting would be a good test.