Cadillac

Cadillac repair questions? Ask a mechanic for answers ASAP

Connect one-on-one with {0} who will answer your question

This answer was rated:

Cadillac CTS: Why would there be relays missing in the fuse…

Why would there be relays...
Why would there be relays missing in the fuse box? 2008 cadillac CTS. Third brake light not working. Tried to follow the step action test but no bass in the fuse box?
Show More
Show Less
Ask Your Own Cadillac Question
Answered in 12 minutes by:
2/28/2015
Cadillac Mechanic: Mark, ASE Certified Technician replied 7 years ago
Mark
Mark, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 847
Experience: 34+ yrs Dealership Exp. - Fully State & ASE Certified - GM Master & GM World Class Tech
Verified
Greetings and welcome to Just Answer. My name is Mark.
Just so we're communicating at the highest level here, I might ask you a few questions so I fully understand what you're talking about. If I should happen to be "offline" when you reply, please give me a chance to respond. I usually will do so with-in 10-12 hrs. (Usually sooner) If I cannot answer your question, or help you to your satisfaction, I will "opt" out and give another tech the opportunity to assist you.
To answer your question directly, "Why would there be relays missing in the fuse box" .... the fuse box is mass produced and applies to multiple make and model vehicles. The same fuse block will work with many different vehicles. When your vehicle is put together, only those relays, circuit breakers, and fuses, are used that apply to YOUR vehicle. That empty relay slot, an empty fuse slot, or even empty screw fastener holes, will be used in other type applications.
With your "third" brake light out, sounds to me like it might just be a burned out bulb(s). You didn't mention that your other brake lights were out. The third brake light should be on the same circuit as your normal brake lights. So if your getting power to your other brake lights, yet the third brake light is not working, make sure the bulbs are okay.
Next, disconnect the connector to the third brake light, and test for power to the connector. Use a 12-volt test light connected to ground, have someone tap on the brake and make sure you have power to the connector.
Before I get too much more involved, let me know if you understand so far, have any further questions, and what you have done so far in testing.
Thank you so much
Ask Your Own Cadillac Question
Customer reply replied 7 years ago

Hey Mark. The other brake lights work. I have a new light and it is not working. I do not have power going to the connector. I connected a tester to the black wire and touched it to the positive battery cable and the tester light up. I connected the tester to the blue wire and touched it to ground and nothing.

Cadillac Mechanic: Mark, ASE Certified Technician replied 7 years ago
Okay, very good. I see you know what you're talking about and have done some good testing. I have done a quick search on my end with the schematics to GM service information, and I see there should be a fuse block in the trunk on the right side. Looks to be a 10amp fuse running that circuit. But, like I mentioned earlier, if your other tail lamps work, the fuse should be good.
I have copied and pasted a schematic from the manual and the link is for Dropbox for you to view. Click on the link and you should be able to see the schematic. You will see that the BODY CONTROL MODULE controls that Center High Mounted Stop Light. Your testing has verified the ground circuit is good but your power circuit is not. Your issue could be wiring from the BCM to the light, or a faulty internal issue within the BCM
https://www.dropbox.com/s/aor64wijy0jp8mp/Stop%20and%20Turn%20-%20Cadillac%20CTS.docx?dl=0
Let me know if you were able to see the schematic and have any further questions. I will do just a bit more research and let you know if I come up with anything more.
**********************
**********************
I was able to find a small chart with the manual with a step-by-step diagnostic. I was right in thinking most likely your issue is the BCM if you don't have any wiring issues. Below is the procedure.
*******************
*******************
Center High Mounted Stop Lamp Malfunction:
Ignition OFF, disconnect the harness connector at the center high mounted stop lamp.
Ignition OFF, exterior lamps OFF, test for less than 5.0 Ω between the ground circuit terminal B and ground.
If greater than the specified range, test the ground circuit for an open/high resistance.
Connect a test lamp between the control circuit terminal A and the ground circuit terminal B.
Ignition ON, turn the stop lamps ON and OFF by applying and releasing the brake pedal. The test lamp should turn ON and OFF when changing between the selected states.
If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
If all circuits test normal, test or replace the center high mounted stop lamp.
Ask Your Own Cadillac Question
Customer reply replied 7 years ago

It sounds like i should just replace the BCM. How do I know which one it is?

Cadillac Mechanic: Mark, ASE Certified Technician replied 7 years ago
Below is a picture. You'll need to a couple panels on the driver's side to gain access.
https://www.dropbox.com/s/baj95cronwcrwtc/Body%20Control%20Module%20Replacement.docx?dl=0
Once it is replaced, it will need to be programmed of course. Each BCM is specific to the vehicle.
Ask Your Own Cadillac Question
Customer reply replied 7 years ago

Wouldnt it be easier to runa jumper wire from the brake lights to the blue wire for third brake light?

Cadillac Mechanic: Mark, ASE Certified Technician replied 7 years ago

I know that sounds simple enough and why wouldn't they wire it that way in the first place, but you might create issues with feedback and your turn signal circuit as well.

When your working with mili-amps for control modules, and the fact that other modules run through for communication, you'll want to be careful when connecting and splicing wires.

Mark
Mark, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 847
Experience: 34+ yrs Dealership Exp. - Fully State & ASE Certified - GM Master & GM World Class Tech
Verified
Mark and 87 other Cadillac Specialists are ready to help you
Ask your own question now
Was this answer helpful?

How JustAnswer works

step-image
Describe your issueThe assistant will guide you
step-image
Chat 1:1 with a cadillac mechanicLicensed Experts are available 24/7
step-image
100% satisfaction guaranteeGet all the answers you need
Ask Mark Your Own Question
Mark
Mark
Mark, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 847
847 Satisfied Customers
Experience: 34+ yrs Dealership Exp. - Fully State & ASE Certified - GM Master & GM World Class Tech

Mark is online now

Related Cadillac Questions
What is the trans pump fuse under the hood in the fuse box
What is the trans pump fuse under the hood in the fuse box for. The fuse was missing when I bought the car… read more
Don - Mo Lurch
Don - Mo Lurch
Owner
Vocational, Technical or Trade Scho
11,854 satisfied customers
My right daytime running light/ low beam and my aftermarket
My right daytime running light/ low beam and my aftermarket sunroof on my Cadillac CTS 4 with the 3 liter engine both quit operating at the same time, could they be related … read more
HondaPlatinum
HondaPlatinum
Vocational, Technical or Trade School
28,156 satisfied customers
Wiper fluid isnt coming out checked fuses and relays their
wiper fluid isnt coming out checked fuses and relays their ok no noise when pushing button … read more
Jake
Jake
6,731 satisfied customers
Where is the fuse for Cadillac CTS CTS alternator. No I
I tried nothing I want to know where the fuse boxes at … read more
Daniel Chaidez
Daniel Chaidez
Technician
Diploma
5,671 satisfied customers
No low beams on the headlights. Just high beams. All is
Yes . I replaced the low beam relay still don't work. I jump the circuit with a hot wire they will come on. … read more
Mechanic01
Mechanic01
17,095 satisfied customers
2005 Cadillac CTS My brake lights are not working, both
2005 Cadillac CTS My brake lights are not working, both corner lights and third (top) brake light do not work. Bulbs turn red when the lights are on, but they don't flash when i press the brakes. what… read more
Jerry Newton
Jerry Newton
Cadillac Technician
Vocational, Technical or Trade Scho
1,738 satisfied customers
My brake lights do not work I've checked and changed the
My brake lights do not work I've checked and changed the relay the brake pedal switch the bulbs and I had a burnt socket that I replaced also any suggestions or anything would be greatly appreciated … read more
Dan
Dan
Automotive Technician
Vocational, Technical or Trade Scho
25,009 satisfied customers
2006 Cadillac cts brake lights don't work I checked the
2006 Cadillac cts brake lights don't work I checked the fuses, relays and bulbs … read more
Dan
Dan
Automotive Technician
Vocational, Technical or Trade Scho
25,009 satisfied customers
The tail lights work but no brake lights. 07 cts. The
The tail lights work but no brake lights JA: Have you checked the bulbs? Have you checked the connection? Customer: Yes JA: What is the model/year of your Cadillac? Customer: 07 cts JA: Are you fixing… read more
Chad Farhat
Chad Farhat
Owner
Associate Degree
11,883 satisfied customers
My instrument cluster, the radio and the front signal light
My instrument cluster, the radio and the front signal light don t works … read more
eric remington
eric remington
FORMER SHOP OWNER/TECHNICIAN/INSPECTOR
associates degree
1,610 satisfied customers
I HAVE A 2008 CADILLAC CTS WITH HIGH INTENSITY LIGHTS. THE
I HAVE A 2008 CADILLAC CTS WITH HIGH INTENSITY LIGHTS. THE HI AND LOW BEAMS ARE NOT WORKING, YET THE OTHER LIGHTS ARE ON. THE POWER WAS CHECKED AND THERE WAS NO POWER COMING FROM THE FUSES HOWEVER THE… read more
sprinkles08
sprinkles08
Technician
High School or GED
19,946 satisfied customers
Pete. I have a 2009 Cadillac CTS. Trunk release works
Hi Pete. I have a 2009 Cadillac CTS. Trunk release works sometimes and other times not. I would like to change the Trunk Release Relay, however I can't find it! The OM indicates in the trunk left side… read more
sprinkles08
sprinkles08
Technician
High School or GED
19,946 satisfied customers
Cadillac CTS: Having issues with my 08 cadillac cts the left
Having issues with my 08 cadillac cts the left turn signals stopped working. Im also not getting the indicator on the dash. Hazards are working fine. Checked rear fuzes and relay which all seem to be … read more
BOBBYSS
BOBBYSS
Automotive Repair/Damage Investigator
Associate Degree
14,739 satisfied customers
Cadillac CTS: Brake lights not working on my 06 caddillac cts
Brake lights not working on my 06 caddillac cts but the center brake light on the trunk is working… read more
Dave Nova
Dave Nova
Cadillac Technician
Associate Degree
1,522 satisfied customers
Cadillac SRX: I have a 2004 Cadillac SRX my turn signals are
I have a 2004 Cadillac SRX my turn signals are working but my break lights are out. What could be the problem? Can anyone help?… read more
ZZDaryl
ZZDaryl
Lead Auto Tech
Some college and advanced training
11,511 satisfied customers
Cadillac CTS: I have a 06 CTS Cadillac (Brake Lights Stay-On),
I have a 06 CTS Cadillac (Brake Lights Stay-On), I have changed brake lite switch but lights still stay on?… read more
Pete
Pete
Automotive Diagnostic Specialist
General auto certifications
38,515 satisfied customers
Cadillac: rear brake..fuses..the brake light on the trunk does work
my cts cadillac rear brake lights don't come on, i checked the fuses and they are okay - the tailamp is okay, but when i brake the light does not come on the brake light on the trunk does work… read more
Mark
Mark
ASE Certified Technician
Associate Degree
847 satisfied customers
I have a 2006 Cadillac Cts. The brake lights went out, but
I have a 2006 Cadillac Cts. The brake lights went out, but the center strip light is still working. All other tail lights are working. The bulbs and fuses appear to be fine. The manual dosen't seem to… read more
John
John
MASTER AUTOMOTIVE TECHNICIAN
2 YEARS COLLEGE
9,106 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here.

DianeDallas, TX

< Previous | Next >

Meet the Experts:

Jerry Newton

Jerry Newton

Cadillac Technician

1,738 satisfied customers

ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.

Dave Nova

Dave Nova

Cadillac Technician

1,522 satisfied customers

ASE Master Certification. GM World Class Certification

Chris (aka- Moose)

Chris (aka- Moose)

Cadillac Technician

1,158 satisfied customers

24 years of experience diagnosing & repairing

George H.

George H.

ASE Certified Technician

792 satisfied customers

ASE Master Tech 15+ Years

Tim Mohr

Tim Mohr

ASE MASTER TECH

588 satisfied customers

30 YRS EXPERIENCE, FOREIGN AND DOMESTIC, GAS AND DEISEL

Mike S.

Mike S.

ASE Certified Technician

570 satisfied customers

ASE certified

Ivan

Ivan

ASE Certified Master Technican

219 satisfied customers

ASE Master Tech w/ 20+ years in the field. Self employed for 9 years. Member of AUTOLAB radio show.

< Previous | Next >

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x