Car

Ask a Mechanic Online and Get Answers to Your Car Questions

Ask an Expert,
Get an Answer ASAP!

Car
This answer was rated:

Pontiac G6: Rear brake lights work the reverse..malfunction..dashboard

My Pontiac G6 has the...
My Pontiac G6 has the same brake light problem as in other web posts: Rear brake lights work the reverse of how they should. No sign of malfunction on dashboard. While key is on, brake lights are on. When pedal is pressed brake lights go out. I don't have schematics so can't see if a brake relay shorted/grounded terminal could be the cause. Other web posts suggest the (expensive) Body Control Module is the problem, but I have found no confirmations. One web post said the problem occurred after replacing brakes (could have happened, I didn't notice when mine were replaced); if so, then I assume some sensor is calibrated after the dealership replaces brakes (mine weren't replaced by a dealer).
Show More
Show Less
Ask Your Own Car Question
Answered in 2 hours by:
10/18/2008
wrench9124
wrench9124, ASE Certified Technician
Category: Car
Satisfied Customers: 3,432
Experience: GM Master Certified, ASE Master Certified, 32 years exp, GM Hybrid Certified, GM Mark of Excellence
Verified
Hello, and welcome. you are thinking right here. the brake lights on turned on by the Body control module. the BCM receives a class two signal from a brake position sensor mounted on the brake pedal. and yes this brake position sensor has to calibrated with GM tech scan tool!!! along with the wiring diagram, do you need a detail function description on how the lights work??
Ask Your Own Car Question
Customer reply replied 9 years ago

Yes, along with the wiring diagram, a detailed functional description would be fantastic, better than the source code! A flow chart would work just as well, too.

 

The brake petal height is adjustable by a control next to the steering wheel (I've never tried it). If the pedal height has to be adjusted after brake pad replacement, I would expect the mechanic to use this adjustment and not monkey with anything else around the pedal. I assume the pedal height control is designed to allow pedal adjustment without throwing calibration around the pedal out of whack. So I would think the only thing that needs calibration is near the brake actuators at the wheel, or maybe in the ABS module. Is there something to adjust at either location?

The only adjustment, is what is called a brake sensor recalibrate. this is only usually done after the switch has been replaced or some sort of reprogramming has been done. here is the wiring diagram, and how the system works along with the calibration. but keep in mind, the ONLY WAY, this can be ajusted or reclaibrated is with a GM TECH SCAN tool.

 

If there is anything else I can answer, please feel free to ask!!!

 

 

Object Number:(NNN) NNN-NNNN Size: FS

 

 

The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, transmission control module (TCM), engine control module (ECM), and stop lamp relay coil side. When the stop lamp relay receives battery voltage from the BCM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage through the STOP LP fuse to illuminate the center high mounted stop lamp (CHMSL).

 

The brake pedal position sensor (BPPS) receives a low reference signal and a 5-volt reference signal from the BCM. Whenever the brake pedal is applied, the BPPS applies a variable voltage signal to the BCM through the stop lamp switch signal circuit. The BPPS calibration must be performed after the BPPS or body control module (BCM) have been serviced. The calibration procedure will set BPPS home value. This value is used by the BCM to determine the action of the driver applying the brake system and to provide this information to the vehicle subsystems via the class 2 communication bus.

Brake Pedal Position Sensor Calibration

  1. Install a scan tool.
  2. Select Diagnostics.
  3. Turn ON the ignition, with the engine OFF.
  4. Select the vehicle.
  5. Select Body and Accessories.
  6. Select Lighting Systems.
  7. Select Module Setup.
  8. Select BCM.
  9. Select the BPPS calibration procedure and follow the directions displayed on the screen.

 

wrench9124
wrench9124, ASE Certified Technician
Category: Car
Satisfied Customers: 3,432
Experience: GM Master Certified, ASE Master Certified, 32 years exp, GM Hybrid Certified, GM Mark of Excellence
Verified
wrench9124 and 87 other Car Specialists are ready to help you
Ask your own question now
Customer reply replied 9 years ago

Thanks. Sounds like I will have to take the car in to get the brake pedal position sensor calibrated.

 

I'm tempted to make the adjustment myself, experimenting until the lights come on at the right pedal movement. Considering the current behavior of the brake lights, I don't have anything to lose.

yes, that would be your next step, especially if the sensor has been moved.

 

I hope I have been helpfull, and if you have any other questions, Please feel free to ask!!

Ask Your Own Car Question
Customer reply replied 9 years ago
Where is the Brake Pedal Position Sensor? You have a picture?

sure, here is a picture.

 

Above Brake Pedal


Object Number:(NNN) NNN-NNNN Size: MF

(1)Brake Pedal Position Sensor
(2)Adjustable Pedals Position Sensor

 

Object Number:(NNN) NNN-NNNN Size: SH

 

Ask Your Own Car Question
Ask wrench9124 Your Own Question
wrench9124
wrench9124
wrench9124, ASE Certified Technician
Category: Car
Satisfied Customers: 3,432
3,432 Satisfied Customers
Experience: GM Master Certified, ASE Master Certified, 32 years exp, GM Hybrid Certified, GM Mark of Excellence

wrench9124 is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

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:

I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry.

Stephanie PElm City, NC

used your service this weekend with "Trecers" help. thank you ,thank you, thank you. replaced an A/C fan motor. Local Auto Zone had part. $15.00 "tracer" fee and $40.00 for parts, I saved several hundreds of dollers at a shop. i will recommend you and use you in the future.

David L.Richmond, TX

9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much.

PhilMarysville, CA

Lurch. Thank you very much. I had real doubts about this website but your promptness of response, quick followup and to the point answer with picture was incredible.

CharlesWalnut Creek, CA

As a single woman, I really appreciate an excellent and affordable opinion.
Thank you Geordie, I will not hesitate to contact justanswer in the future!

SueCharleston, WV

Another great insight to what may be the problem. I will have my mechanic take a look at it tomorrow. Thanks again, Frank...you do indeed know your stuff.

JimCastleberry, FL

The nearest Volvo dealer is 160 miles away. Best $15 bucks I have spent in a long time!

Paul MCorpus Christi, TX

< Previous | Next >

Meet the Experts:

Chris (aka-Moose)

Chris (aka-Moose)

Technician

1,243 satisfied customers

16 years of experience

Ted G.

Ted G.

ASE Certified Technician

1,724 satisfied customers

20 years auto repair experience, ASE Master Tech, Mechanical Failure consultant, Expert Witness

George H.

George H.

ASE Certified Technician

1,537 satisfied customers

ASE Master Tech 15+ yrs, AAS Automotive Technology, Factory trained Asian specialist

GM Tech (Cam)

GM Tech (Cam)

Auto Service Tech

669 satisfied customers

GM Grand Master Technician 2007. 14 years experience.

Amedee

Amedee

Former ASE Master Tech

2,520 satisfied customers

ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector

Jerry

Jerry

Master Mechanic

2,181 satisfied customers

ASE master, 30+ years. All makes and models. Trouble shooter, shop forman, service manager

Richard

Richard

ASE Certified Technician

1,000 satisfied customers

12 years Ford Lincoln/Mercury Jaguar dealership as a technician and shop foreman reparing all makes

< Previous | Next >

Related Car Questions
I have a 2008 GMC acadia the fuel pump does not come on and
i have a 2008 GMC acadia the fuel pump does not come on and it will not turn over nor do nothing … read more
Amedee
Amedee
Former ASE Master Tech
Vocational, Technical or Trade Scho
2,520 satisfied customers
Leaky oil cooler 2005 TDI Passatt 2.0. Yesterday. 2005 2.0
Id like to i have the "O" rings but i cannot find a parts detail of the assembly. the oil cooler attaches just below the oil filter houseing. there is what looks like approximately a 30 millimeter nut at the bottom of the oil cooler. Id like to see a cross section of the assembly … read more
Kevin
Kevin
workshop foreman /master tech/mot tester
0 satisfied customers
Need detailed instructions from a service manual to remove
Need detailed instructions from a service manual to remove and install the heater core from a 2011 jeep grand Cherokee 5.7 engine.… read more
Eurocar Inc
Eurocar Inc
Master Audi/VW Tech
Associate Degree
1,773 satisfied customers
2016 Malibu Ls with there new 1.5L turbo 17,000 miles is
2016 Malibu Ls with there new 1.5L turbo 17,000 miles is over heating can we talk on phone due to complexity of how this started. Btw I paid last question for personal call and never received it. See … read more
eauto
eauto
self employed
High School or GED
74 satisfied customers
Need to know how to use a jump cable to start a dead 2001
Need to know how to use a jump cable to start a dead 2001 xj8 jaguar using another car as a booster … read more
Stephen, MBA
Stephen, MBA
Master's Degree
166 satisfied customers
Need to replace lights for speedometer for a 2008 infiniti
need to replace lights for speedometer for a 2008 infiniti g35S … read more
Stephen, MBA
Stephen, MBA
Master's Degree
166 satisfied customers
I have a 99 Bentley Arnage and the seatbelt was pulled out
I have a 99 Bentley Arnage and the seatbelt was pulled out all the way and won't got back in. How do I fix this? … read more
Gabriel Grey
Gabriel Grey
Master Service Technician
Associates
378 satisfied customers
2017 R8 v10 plus battery went deAd and I cannot get into
2017 R8 v10 plus battery went deAd and I cannot get into luggage compartment to charge the battery. Is there a manual release… read more
Stephen, MBA
Stephen, MBA
Master's Degree
166 satisfied customers
When considering the Carfax details of these two used MINI
When considering the Carfax details of these two used MINI Cooper cars:http://www.miniofmarin.com/detail-2013-mini-cooper_hardtop_2_door-base-used-16592946.htmlhttps://shift.com/car/c192808?utm_source… read more
Kavey
Kavey
86 satisfied customers
My hazard lights suddenly went on overnight and couldn't be
My hazard lights suddenly went on overnight and couldn't be turned off. I held the hazard switch down and they stopped. I stuck it down for the rest of the night and this morning, they had switched of… read more
Michael Solis
Michael Solis
363 satisfied customers
Can you send me detailed instructions on how to remove and
can you send me detailed instructions on how to remove and replace the driver side power window regulator on a 2006 GXP Gran Prix?… read more
eurotec
eurotec
Vice President / Manager
Associate Degree
11 satisfied customers
Something with the electrical system. 2003 suzuki xl7. All i
no, i do not know enough to know the questions to ask… read more
Chris (aka-Moose)
Chris (aka-Moose)
Technician
Vocational, Technical or Trade School
1,243 satisfied customers
I'm about to pick up my new 2017 Grand Cherokee Limited and
I'm about to pick up my new 2017 Grand Cherokee Limited and the dealership called to say there is discoloration on the bumper. They said they are going to sand it and re-paint. Is that okay or should … read more
Edward Clayton
Edward Clayton
Associate Degree
1,033 satisfied customers
Question is related to a 2006 Subaru B9 Tribeca, the
Hi. Question is related to a 2006 Subaru B9 Tribeca, the driver's side digital climate control rounded temperature selector. We had the vehicle recently detailed, and the detailer must have broken the… read more
sprinkles08
sprinkles08
Technician
High School or GED
11 satisfied customers
I am trying to find detailed information for removal and
Hello, I am trying to find detailed information for removal and replacement of rear hub assembly on 2007 Suzuki XL7. … read more
Ron Z.
Ron Z.
Vocational, Technical or Trade Scho
2 satisfied customers
Assistant: Thanks. Can you give me any more details about
Matthew Assistant: Thanks. Can you give me any more details about your issue? Customer: I just changed my wife brakes and the trac off light is on.… read more
David Craig
David Craig
OWNER/MECHANIC
Associates
4,429 satisfied customers
Moose, Assistant: Thanks. Can you give me any more details
Moose, Assistant: Thanks. Can you give me any more details about your issue? Customer: Wife was driving our 04 Odyssey yesterday. Throttle acted like it was stuck open. Very scary.… read more
Pete
Pete
Independent Auto Technician
Vocational, Technical or Trade Scho
138 satisfied customers
I'm looking for a detailed diagram or exploded view for
I'm looking for a detailed diagram or exploded view for replacing the antenna base on a 2010 Convertible Mini.… read more
heavy_chevy_396
heavy_chevy_396
Vocational, Technical or Trade Scho
2,518 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.

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