High mounted stoplight does not work

Tiny
GEORGE LARSEN
  • MEMBER
  • 2012 FORD MUSTANG
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 62,000 MILES
My high mounted stoplight on my mustang does not work. It is LED and I have replaced with a new one. There is power to the connector that connects to the light and It still will not work. I find no fuses either under the dash or in the engine wall that appear to be associated with this light. I am at a loss. I called Ford and they say that it looks like a computer module located in the engine compartment but the computer module which is a large 20 amp fuse test good. Please help.
Wednesday, November 15th, 2017 AT 2:44 PM

4 Replies

Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,005 POSTS
I am looking at a 2011 diagram.

See if things look the same!

The third light is tied to the driver's side brake light wire.

It is powered through fuse 11 in the passenger side fuse block (12 is passenger side).

Sending you the diagram (see left side). The legend is at the very top to identify the parts (like "5" is the passenger fuse box).

I placed some purple arrows in there.

Check your grounds!

Keep us posted.

The Medic
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Wednesday, November 15th, 2017 AT 3:27 PM
Tiny
GEORGE LARSEN
  • MEMBER
  • 2 POSTS
This is completely different than mine and the names do not even match up with what my manual says.
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Wednesday, November 15th, 2017 AT 4:08 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,005 POSTS
I will message another expert and see if he can get the 2012 diagram.

The Medic
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Wednesday, November 15th, 2017 AT 4:24 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,998 POSTS
The 2012 Mustang CHMSL is fed directly from the body control module. The BCM gets the signal from the brake switch and turns it on. No fuses in the circuit.

If you have power on the yellow/gray wire but no light, check the black/white ground wire to see if it has continuity to the chassis. Check the wiring harness right near the trunk hinge arm where it flexes as the trunk moves, the wires like to break in the harness, Do not bother trying to solder them together at the break. Go back to an area in the harness that does not move and run a new wire. You probably will end up running both just as prevention of the power feed breaking.
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Wednesday, November 15th, 2017 AT 6:50 PM

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