Wire Harness Burnt Wire
 

Hi I've got a 2013 Scion FR-S and the car is at a shop right now getting a carbon hood paint matched and a new bumper. The owner of the shop called me this morning to let me know that when they started the car with the hood off, they smelled a faint burning smell, so they took a look and noticed a green wire on the main wire harness was burnt and smoking. Any ideas what might be causing this, and any recommendations on fixing it? Could a wire be pinched and it's causing a short? I've included a couple of pictures and would appreciate any opinions or help!

Pull the schematic, Ultramaroon has it in his sig. See what it goes to, it's hard to tell from the picture but pre 17' cars should be the same. If you unplug the connector you can check the pin for continuity to ground, if it is not supposed to have ground it is pinched/chafed somewhere, or whatever it is connected to is shorted and it needs repaired.

My question is this:

Besides the Edelbrock supercharger, what other aftermarket modifications have been made to the car?

Electrical wise I have spec d headlights, Valenti taillights, and aftermarket side markers.

Then I would check the wiring schematic as @NoHaveMSG said that @Ultramaroon has a link to on his signature to see if anything related to any of your aftermarket equipment is running through that connector.

Hi and thanks for the info! I looked at the wiring schematics and believe I read them correctly. The body shop told me it's a green wire and according to the schematics it's at the AC1 connection and appears to be for a Knock Control Sensor (I've included some screen shots of the schematics). I'm a little puzzled why this wire would burn now, I did drive the car to shop with the hood off and was wondering if it's possible that the wind made the connection loose and caused the wire to burn? The only other thing I could think of before the wire burned was the shop did start the car with the bumper, headlights, and some other wires disconnected before they smelt the wire burning. But I don't believe that would cause the wires to burn. Thanks for all the info

Images:
https://imgur.com/a/NZVlAOQ

Hi I appreciate the help! From the wiring schematics the connection is AC1 and the shop told me it's a green wire which on the schematics appears to be for a Knock Control Sensor, so I don't think anything aftermarket would be affecting it. Its puzzling me why this wire would burn up now!

Unplug the connector and verify which pin. There are multiple green wires there and that one looks on the second row, but I can't tell. Knock sensor is 5vdc and barely any amps. Shouldn't have burned a wire on the chassis side of the plug from a knock sensor.

I hate to say this, but the entire harness is a ticking time bomb. For those that do not know, OEM harnesses are mass-produced and made with cheap materials in order to save on production costs.

I am currently rewiring my entire BRZ for a multitude of reasons, however, in doing so, found many wires that were knicked and/or cut, which were simply just wrapped with more electrical tape.

I never did trust the manufacturer's wiring harnesses simply because it's cheap labor lol.

Anyway, not saying that is the culprit, but I would not doubt that this could have been a part of the issue.

What they've done to one, you know they've done to more.

Either way, hope your problem is solved now, but just some food for thought.

Let's not get too dramatic about this. There's nothing inherently wrong with the harness. Regardless of the function of that specific lead, it burned only on the chassis side of the connector. The issue is right there. Did someone unplug it and then jam it together with a bent pin? I've never had that particular connector apart but I suspect a short to ground.