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Old 02-12-2019, 12:55 AM   #1
Scooby Newbie
Member#: 496758
Join Date: Jan 2019
Default Help me Identify What This Wire Does? 2017 WRX

I need help identifying what the blue wire (in the images below) is for on my 2017 WRX Premium. I noticed that there were bite marks on the plastic casing around the wires coming from the negative battery terminal. After opening the plastic casing the blue wire has a huge chunk removed and the white wire was started to be chewed on. I have absolutely no issues with anything in my car, but was still curious what this wire could be for.

I took the car to a local Subaru dealership and was told that it was just a ground wire and the only thing that was happening now that it was chewed off is that the circuit is running in a different way. They wanted $300 to splice it or $550 to replace the negative battery cable.

I called around to some other dealerships and found one that would replace the negative battery cable for $350. After dropping my car off there, they called me and said that the negative battery cable is not what needed replacing and that I would have to replace the bulk head harness for approximately $3k. WHILE THERE IS STILL NOTHING WRONG WITH THE CAR. This dealership explained that they think the missing wire is to show a warning light when the battery has low voltage. I picked up my car without having them do any work and took it to Autozone for a diagnostic. No codes were thrown from the diagnostic they ran.

So I am hoping that someone on here can help me to identify what the purpose of this chewed up wire is since two Subaru dealerships had different opinions and nothing is wrong with the car when this wire is not functioning.

TLDR: Rodent chewed through blue wire below. Want to figure out what the wire is for.



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Last edited by jarmy16; 02-12-2019 at 01:09 AM.
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Old 02-12-2019, 04:54 AM   #2
Trust no one
Member#: 11170
Join Date: Oct 2001
Chapter/Region: Tri-State
Location: NYC
02 WRX
15 WRX/05 GTO


That is for the battery sensor attached to the negative terminal. The sensor monitors the charge/discharge current and battery temperature. The car will run normally with that wire broken, but charging regulation will be affected and there may be codes set although you might not see the check engine light.
It definitely should be repaired. From your pics it appears there is enough intact wiring left at the sensor to splice in new sections of wire to replace what was damaged, if this is done properly (solder/heat shrink tubing/wrap with 3M electrical tape) it should work properly and hold up.
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