[wrexxin97]

Hey all,

I bought a new set of LED tail lights to replace my dead bulbs and get an inspection done, but I have run into an issue: The lights wont go on. No bulb no matter which ones I put in won't work. So, I am wondering what are the possible causes. I checked fuses up by the battery and they seem to be good. So, I am wondering what the problem might be. I have had these things out for about a year so they haven't seen working bulbs in a long time, but I just want to be sure I am looking at everything correctly and not misdiagnosing and banging my head against the wall.

Thanks guys!

 

[wrexxin97]

also, just wanted to give a little bit of additional info,

the trunk lights that illuminate the trunk itself function
my third brake light works and always has
I just checked the fuse that shuts off the trunk light by the battery, and so I don't believe it is the fuse at least on that side
the led lights do work because if i touch them to where the trunk light goes, they illuminate

So, the only two scenarios I can think of being wrong is either my harness itself is bad, or that theres a fuse under the dash that might be bad.

*Strike that - I just checked the fuses under the dash and all of them appear to be in good shape. Which may be pointing to my harness being bad. I'm not sure if there's anything else I can check.

If anyone can think of something i'm missing, then please let me know.

 

[SoCal2V]

Do you have something you can check for power with, either a test light or voltmeter? I would probe the terminals in the lamp sockets and see what happens. Obviously make sure the headlamp switch is pulled out one click while testing.

Those sockets that you snap the lamps into are made of dome sort of rubber material, I have seen in the past where they can become a bit scorched from a hot lamp and the terminals get a little cooked/corroded/warped and no longer make good contact. One of the license plate lamps on my truck suffers that problem; if I have the bulb in there just right it works but as soon as I hit a bump it goes out.

At any rate I would focus your efforts around the sockets. If no voltage, look and see if maybe one of the wires feeding into the socket looks broken.

 

[mustangmattjj]

did you ever figure this issue out? i am at the same issue and ooint original postor was at on my 03 mustang 4.6l manual. just noticed lic. plate bulbs out. removed bulbs switched with working trunk light bulbs are fine. checking with volt meter now, intially sought on my google search for the fuse location and ofcourse saw many threads stating there is not an individual one and the smart system SJR or whatever that regulates a couple different things may have glitched and causing the issue. hoping thats not the case

 

[AndyEckel]

The license plate lamp bulb does not have its own fuse. It is on the same circuit as other rear lights.

Since all the other lights are working normally, and since you know the bulb is good, I would absolutely suggest you start peeling back the wiring harness from that bulb. Your problem lies between that bulb and wherever it is spliced into. Probably somewhere in the trunk.

There will only be two wires: 12V power and ground. You are looking for a chaffed spot where the wire sheath has rubbed through and the wire itself is touching metal. A split. Check also pin fitment on the connector.

Get yourself a "seam ripper" from Hobby Lobby. It's a $5 sewing / quilting tool and makes cutting through the loom and wrapped electrical tape a breeze.

Absolute worst case scenario is running two new wires from your tail lights. HTH!

Best wishes!

 

[Cobrajet67]

did you ever figure this issue out? i am at the same issue and ooint original postor was at on my 03 mustang 4.6l manual. just noticed lic. plate bulbs out. removed bulbs switched with working trunk light bulbs are fine. checking with volt meter now, intially sought on my google search for the fuse location and ofcourse saw many threads stating there is not an individual one and the smart system SJR or whatever that regulates a couple different things may have glitched and causing the issue. hoping thats not the case

Simply look in your owner's manual for fuse locations... Also, I wouldn't have piggybacked onto a 7 year old thread. These members in this ancient thread haven't been around for a long time. You're lucky to have gotten answers.
You have fuses for the reverse lights, high beams, left low beam, right low beam, headlights in general, 2 fuses for the brake lights, foglights, and parking lights but nothing that's got the license plate light specifically on its own circuit. It's wired into the parking light circuit. If the taillights light up then you have power going back there and the problem lies in the wires that branch off for the license plate lights. You probably have a bad ground or a break in the wires to the license plate lights somewhere coming off the main light harness.
A 2003 doesn't have an SJB. That's a term for 2005+ Mustangs and other newer Ford vehicles. You just have a regular BCM/GEM and there likely won't be a separate wire to the license plate lights from it.