this once has really gotten me! Out of the 4 rear brake lights the closest to the trunk emblem on the passenger side is out. The first thing I thought was that it might be burnt out so I swapped out the light but no luck . Then I thought it might have been something to do with the wiring because I has cut into the reverse lights to wire a backup camera - I checked and all the wires and connections and everything was intact like it had been for the last 7 months (backup camera still works, no issues). I couldn't find anything wrong except the light just stopped working .

Although, I did wash the car with the garden hose just before the light stopped working, I didn't wash under the hood or anything, although I did spray where the drains below the windshield wipers are, do you guys think it could be a short? I usually use a power washer and blast the whole thing so I kinda think it's weird that the garden hose got anything electrical wet? :P

Are there any fuses or things I should check? It's been about 18 or so hours since the light stopped working if it matters

Thanks!!

 

Check the owners manual for a fuse listing. But my guess is water got into the smart junction box ( fuse box in passenger foot well). It's a common problem in these cars. Take the fuse box cover off and look inside to see if there any trace of wetness.

 

Trace the wire from the light and check for where power is lost at using a digital volt meter.

 

When I pulled the blue connector (in picture) out all the brake lights, head lights etc came on (including the one that wasn't working) but as soon as I plug it back in and try the brake light still that single one does not come on

I checked the junction box and all under the passenger side for any trace of water and if there was any water it wasn't evident

 

Is it just the brake light that doesn't work? Does the running light come on at all for that lamp, or does the bulb not light up at all?

And when you pull the blue connector, do both filaments light up on the suspect lamp? or is it just the running light? Just trying to fully understand the problem.

There could still be water in the SJB, and over the next couple days it could dry out and go back to normal. I've had weird stuff happen with my tail lights not responding to the headlight switch when it gets wet.

 

Thanks for the reply

The running light on the bulb does come on, but when I hit the turn signal the other filament doesn't flash like the light next to it

When I unplug the blue connector the running lights on all the brake lights come on but the turn signals don't work without it plugged in

 

Forgot to attach picture

 

Good pic. So looking at the wiring diagrams, the running light (tan/red) wires are tied together, so if one works they all work (makes sense). The brake light wires (red/white) look like they go all the way back to the SJB and look like separate circuits. The lamps are labelled as RIGHT REAR PARK/TURN LAMP #1 and #2, which the red/white wires are labelled 7 & 6 respectively. I'm not sure what those numbers are (probably internal reference numbers to the diagrams).

Just for reference:

Code:

REAR PARK/TURN LAMPS:

Lamp	Light	Color	 	Number in diagram
RR#1	PARK	TAN/RED	 	9
RR#1	TURN	RED/WHT	 	7
RR#2	PARK	TAN/RED	 	9
RR#2	TURN	RED/WHT	 	6

RL#1	PARK	DRK BL/YEL	13
RL#1	TURN	WHT/RED		12
RL#2	PARK	DRK BL/YEL	13
RL#2	TURN 	LT BL/ORG	11


SJB LABELS:
BLOCK LABELLED AS C2280D

RR TURN LAMPS FEED	1783	RED/WHT 40 (Think the '40' is the pin on module C2280D)
RR TURN LAMPS FEED	1783	RED/WHT 47 (Think the '47' is the pin)

I would see if you can read a module number "C2280D" on the SJB and see if you can probe those pins with either a test light or voltmeter. I don't know what the '1783' is, maybe a relay in the high power distribution box. This wiring diagram sucks compared with what I have for my bike, so not entirely sure how to read everything.

 

If stock, the most inboard light on each side were tail lights only. If there is any sequencing involved, then all three should work. If no sequencing and they still had brake lights there, then someone may have jumped the brake wire signal to the inner light sockets.

 

I think he means passenger side inner brake light.

.

 

Did anyone ever figure this out, I'm having the same problem and would rather not take it to a dealer for this. Any suggestions, no trace of water near the passenger side Junction box, new bulbs in back and still nothing?
08 mustang 4.0 base.

 

The factory has the 6 tail light bulbs set up so all 6 are parking lights but only the 2 outer bulbs on each side are brake/blinker bulbs.

If you install aftermarket wiring that makes the blinker bulbs sequential in the back, it activates all 3 bulbs per side and you'd get this:

 

I know that, one of my brake light, the inner most brake light and blinker does not work and I've checked bulbs and the wiring looks good just haven't been able to Volt test the harness yet, was looking for any other option it could be.