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Daniel Jones
Daniel Jones,
Category: Cadillac
Satisfied Customers: 498
Experience:  GM A Tech at Straub Buick GMC
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2005 STS- Corner brake lights do not function. Center brake

Customer Question

2005 STS- Corner brake lights do not function. Center brake lights works properly. Checked fuse and mini-relay under back set. They're OK.
Turn signals work, 4 way flashers work. Same bulb does not function when brakes applied.
How to fix?
Submitted: 10 months ago.
Category: Cadillac
Expert:  Daniel Jones replied 10 months ago.

Hello. Welcome to the site. Thanks for coming. I'm ***** *****.
I'm here to provide as much information and insight as I can, to best answer your question.

Do you have power to the Stop Lamp Fuse when the key is on and the brakes are applied?

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Customer: replied 10 months ago.
I will check when I get the car back- It's in the shop now till next Tuesday. Can yoiu give me your ideas if there is no power? or what if there IS power ideas? Thanks
Expert:  Daniel Jones replied 10 months ago.

Here is a circuit description. Also you will find attached is the wiring and diagnostic chart.

Stop Lamps

The brake pedal position (BPP) sensor is used to sense the action of the driver application of the brake pedal. The BPP sensor provides an analog voltage signal that will increase as the brake pedal is applied. The instrument panel module (IPM) provides a low reference signal and a 5-volt reference voltage to the BPP sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the IPM will apply battery voltage to the center high mounted stop lamp (CHMSL), transmission control module (TCM), engine control module (ECM), and stop lamp relay. When the stop lamp relay receives battery voltage from the IPM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage through the stop lamps fuse to illuminate the stop lamps. Ground for the left stop lamp and CHMSL is provided at G402 and the right stop lamp is grounded at G401. The stop lamps consist of red lenses and light emitting diodes (LED) instead of incandescent bulbs. The stop lamps on this vehicle will not illuminate unless the ignition is in the accessory, run, or crank positions. When the ignition is in the OFF position, the stop lamps will not illuminate when the brake pedal is applied.

If you need more help, please use the "Reply" tab to continue our conversation - I'm happy to answer follow-up questions.

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Expert:  Daniel Jones replied 10 months ago.

If you need more help, please use the "Reply" tab to continue our conversation - I'm happy to answer follow-up questions.

If you have no follow-ups at this time, please remember to Rate My Service.

Thank you for posting your question.

Your business is very valuable to us.
Thank You

***** *****