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Pete
Pete, Cadillac Technician
Category: Cadillac
Satisfied Customers: 27112
Experience:  17 years Cadillac experience as a technician.
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Installed a replacement right brake light (entire light)

Customer Question

Installed a replacement right brake light (entire light) after a car wreck. The blinker, hazards and running lights work on both sides R/L brake lights, the third brake light works but the brake lights on the R/L brake lights do not. I have changed out a fuse in the underhood fuse box,and check the rear under seat boxes as well.
JA: Have you checked the brake fluid? How's the level and when was it last changed?
Customer: Not recently, no.
JA: What is the model/year of your Cadillac?
Customer: 2006 Cadillac STS
JA: Are you fixing your STS yourself? What have you tried so far?
Customer: Yes, we are. Installed a replacement right brake light (entire light) after a car wreck. The blinker, hazards and running lights work on both sides R/L brake lights, the third brake light works but the brake lights on the R/L brake lightsI have changed out a fuse in the underhood fuse box,and check the rear under seat boxes as well.. plus my husband tested the plug that goes into the brake light, with the car running , and the black/white and green/white wires had power.
JA: Anything else you want the mechanic to know before I connect you?
Customer: Wondering about the park lamp relay micro in front fuse box , #8729, does that effect/work the breaks?
Submitted: 9 days ago.
Category: Cadillac
Expert:  Pete replied 9 days ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Did the brake light issue here only occur after the collision or after the light assembly was replaced?

Let me know so we can continue,thanks Pete.

Customer: replied 9 days ago.
The right tail light was completely broken after the wreck. The left one (driver side) worked, but grew dimmer until now the brake light does not work. After replacing the right tail light, the hazards, blinkers and car alarm setting lights work on both but still not the brake lights. 3rd brake light is functional.
Expert:  Pete replied 9 days ago.

O.k., can you tell me if this is an all wheel drive or rear wheel drive vehicle and which liter or size engine is in the vehicle?

Customer: replied 9 days ago.
V8 4 liter AWD
Expert:  Pete replied 9 days ago.

O.k.,in the right rear fuse panel do you feel or hear the stop lamp relay click when the key is on or when pressing on the brake pedal?

Customer: replied 9 days ago.
I believe I hear the click when I press the pedal, yes
Customer: replied 9 days ago.
Would the BCM module in the underhood fuse box need to be replaced? Looking at the diagram, the park light relay micro #8729 is one of three on that fuse box. BTW: Check the other fuses, all good. Have not pulled the #8729
Expert:  Pete replied 9 days ago.

Do the light blue wires at the tail light assemblies have voltage on them at all?

Customer: replied 9 days ago.
No
Expert:  Pete replied 9 days ago.

O.k.,the light blue is the stop lamp supply voltage.You should have voltage at this wire with the brake pedal pressed and key on.Was it tested this way?

Customer: replied 9 days ago.
it was, my husband worked the voltage meter while I pressed on the brake.
Expert:  Pete replied 9 days ago.

Just to be sure did you make sure the 10 amp Stop Lamp fuse is o.k. in the rear fuse panel as well?

Customer: replied 9 days ago.
Rear fuse panel under the seats?
Expert:  Pete replied 9 days ago.

I believe this panel is under the rear seat on the passenger side.Below is a link to the layout of this panel.Make sure this fuse is o.k.If this is found to be blown replace it and see if they then work.If this is o.k. let me know so we can continue from here.

https://www.dropbox.com/s/252fp6y8y68k5mn/rr-05-15.gif?dl=0

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete