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Discussion Starter · #1 ·
Hi all,

So i've noticed that my rear running lights/marker lights do not work. I've checked bulbs, fuse, relay and they are all good. After testing with the meter it appears there is a short somewhere between the battery and the rear fuse box as everything after the rear fuse box checks out. Just wondering where the most common spots would be to look for the short as I don't have a wiring diagram so anything before the rear fuse box is hard for me to trace.
 

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Discussion Starter · #3 ·
so the park lamp fuse supply is at 0 volts? if true you have a lot of lamps out.
Just the marker lamps in the rear. The brakes, turn signals and reverse lights are all on a different fuse. Only thing on that fuse is the rear marker lights (DRL) and the plate light which is also out and not getting power.

Traced the wires until they go into the rear bumper where I can't see them anymore.
 

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Discussion Starter · #5 ·

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The brake light and parking light are two different filaments.
The reverse light has its own circuit. And the brake lights have their own circuit.
The parking lights also have their own circuit which has a fuse in the trunk fuse box. This supplies front and rear running lights and the license plate light.
The DRL fuse you speak of is for daytime running lights (headlights during the day)

Do your front parking lights work at all? Perhaps the harness got pinched behind the bumper cover...

If the front parking lights are working, but not the rear then you can also check to see if there's any corroded or broken wires behind the fuse box.
You may also have a bad ground back there. I can't say for sure how the coupe is setup, but you may need to remove the rear bumper cover to get a better look at the wiring
 

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Discussion Starter · #7 ·
The brake light and parking light are two different filaments.
The reverse light has its own circuit. And the brake lights have their own circuit.
The parking lights also have their own circuit which has a fuse in the trunk fuse box. This supplies front and rear running lights and the license plate light.
The DRL fuse you speak of is for daytime running lights (headlights during the day)

Do your front parking lights work at all? Perhaps the harness got pinched behind the bumper cover...

If the front parking lights are working, but not the rear then you can also check to see if there's any corroded or broken wires behind the fuse box.
You may also have a bad ground back there. I can't say for sure how the coupe is setup, but you may need to remove the rear bumper cover to get a better look at the wiring
Front lights work fine. I've checked behind the fuse box as well. Everything looks good there. I don't know if I even want to bother taking the rear bumper off at this point. If i had access to a lift I totally would. Taking it to my local mechanic. He's usually pretty good.
 

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(assuming the license plate lamp is working) so if only the rear markers & tails are out the problem should be in the rear fuse block either before or at X2 pin B1 where the park lamp circuit splits into two to supply the left & right sides.
 

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Discussion Starter · #11 ·
(assuming the license plate lamp is working) so if only the rear markers & tails are out the problem should be in the rear fuse block either before or at X2 pin B1 where the park lamp circuit splits into two to supply the left & right sides.
License plate lamp is also out. It was also blown. Replaced it as well. Cars going in later this week so my mechanic can take a look. I hate wiring so much.
 

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12v analog circuits are just not that hard to diagnose.
so now we know your rear markers, tails & license lamp are all out. & you're absolutely sure the front markers are still on when they are supposed to be?
 

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since u already determined the front markers are working that eliminates fuse 6 & relay 27 from suspicion. the problem is after the circuit branches to the rear markers, tails & license plate lamp.
 

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Here's a pic of the backside of my rear fusebox (09 sedan base)



The RED connector has all the wires that go to my rear tail lights.

See the 3 brown wires on the right? One goes to the left rear parking lights, one goes to the license plate light, and the other to the right rear parking lights.

It possible your problem lies right there, likely corrosion on the pin under the connector. If that turns out to be the case, then chances are you have other pins that are starting to get there too....
 

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Discussion Starter · #18 · (Edited)
since u already determined the front markers are working that eliminates fuse 6 & relay 27 from suspicion. the problem is after the circuit branches to the rear markers, tails & license plate lamp.
Only spot I can think of to look would be the section of wiring behind the rear bumper. The wiring i can physically see looks fine until it disappears into the rear. I appreciate the help.
 

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Discussion Starter · #19 ·
Here's a pic of the backside of my rear fusebox (09 sedan base)



The RED connector has all the wires that go to my rear tail lights.

See the 3 brown wires on the right? One goes to the left rear parking lights, one goes to the license plate light, and the other to the right rear parking lights.

It possible your problem lies right there, likely corrosion on the pin under the connector. If that turns out to be the case, then chances are you have other pins that are starting to get there too....
yeah. Mine looks the exact same as that. Everything looks clean as far as I can see. How would I go about cleaning the corrosion if thats whats causing it? Least I can do is that since its easily accessible.
 

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Unbolt the connector and remove it, the act of removing and replacing it should clean it a bit, but you can also spray it with electronics cleaner and add dielectric grease, I'd be careful and make sure nothing has power back there first though.
 
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