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scott, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 1638
Experience:  Caddy man from way back. Interface with on board system as well as scanner.
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I have a 2004 CTS. Both brake lights are not working but the

Resolved Question:

I have a 2004 CTS. Both brake lights are not working but the middle bar light is. The bulbs look fine. Any ideas....thanks!
Submitted: 8 years ago.
Category: Cadillac
Expert:  scott replied 8 years ago.



That is really odd. The lamps are all powered by the same fuse and junction block. To check this out, you will need to access the rear lamps and remove the left rear seat. In there is a fuse box with the BAS fuse and relay, along with a joint connector that splits off to the left/right and high brake lamp. Check voltage at the rear lamps white wire with brake on and see of your getting voltage. If you are, check the black wires to verify your getting ground. The high lamp and the rear lamps do not share the same ground; however, they do share the same voltage.



Customer: replied 8 years ago.

Hmmm....ok. I recently had it in because the motor went out on the back driver side door. This happened after that was fixed...maybe a wire got messed with. I know nothing about cars. We looked at the bulbs and they seemed fine.

Expert:  scott replied 8 years ago.

If you do not have a test lamp, and do not know how to use one, we are going to hit a road block. Considering that this all came about after the repair, and the point of diagnostics takes us to the left rear seat fuse and junction area, I would give the shop a call. If you want to proceed and feel confident, let me know.



Customer: replied 8 years ago.

So is there a fuse that I should check? I can get a test lamp to check the wires.

Expert:  scott replied 8 years ago.
Not a fuse, but a joint connector. First off, I want you to check voltage at the white wires going into the left and right stop lamp sockets with the key on and someone applying the brake. Either one will work for the test at this point. If there is no voltage at one, check the other, remove the seat, and get back with me.
Customer: replied 8 years ago.
Ok, I will have my brother help me out with this on Sunday. I will contact you back then. Thank you, Cindy
Expert:  scott replied 8 years ago.

Cindy, Here you go for a head start.


scott and 2 other Cadillac Specialists are ready to help you
Customer: replied 8 years ago.
Ok, thanks!
Expert:  scott replied 8 years ago.
No problem. I will be out at a 101st Air Born Ranger open house tomorrow, but will check in prior to leaving and when I get back in the evening. No need to reply until I am needed.
Customer: replied 8 years ago.
Hi, we have no power to the brake lights . The ground is fine. Now what do we do?
Expert:  scott replied 8 years ago.



Attempted to get you last night, but there was an issue that would not allow me to open your message. I apologize.


Now I need you to lift the rear seat, drivers side and look at the fuse box. {see what I sent above} Locate the JOINT CONNECTOR and the 4 white wires going into it. All 4 should have power. If any do not, then you have an issue with the connector. If all 4 do have power,then you have a connection issue between the connector and the tail lamps. {high mount lamp is powered off this also, and you stated it works}


Let me know what you find.

Customer: replied 8 years ago.
I brought it into the shop. Hopefully they will listen to me and not retry all the things we tried. Thanks for your help!