Chevy

Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP

Ask an Expert,
Get an Answer ASAP!

Low beam lights won't work. gh beam come and go. Tried

Customer Question
Low beam lights won't work...
Low beam lights won't work. High beam come and go. Tried replacing switches but didn't work. Any ideas?
Submitted: 2 years ago.Category: Chevy
Show More
Show Less
Ask Your Own Chevy Question
Answered in 1 hour by:
2/2/2016
Chevy Mechanic: Daniel Jones,
 replied 2 years ago
Daniel Jones
Category: Chevy
Satisfied Customers: 506
Experience: GM A Tech at Straub Buick GMC
Verified

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.

Did you check to see if you have power to the headlights?

Thank you for posting your question.

Your business is very valuable to us.
Thank You

***** *****

Ask Your Own Chevy Question
Customer reply replied 2 years ago
I have power. Both high and low beams come and go. High works more often than low
Chevy Mechanic: Daniel Jones,
 replied 2 years ago

Here is a description of the Operation of the lights and the wiring diagram.

Headlamps

The headlamp driver module (HDM) is an electronic module that provides electrical power to the vehicle low beam headlamps. The HDM is controlled by a pulse width modulated (PWM) ground signal from the body control module (BCM). The BCM determines the desired lamp intensity using the ambient light sensor, multifunction switch , wiper motor, and the park brake switch as inputs. In general, the HDM will operate in one of three modes:

  • Reduced Intensity Mode: This mode is used by features that do not require or allow maximum low beam headlamp intensity such as daytime running lights (DRL) (nominal: 81% duty cycle).
  • Full Intensity Mode: This mode is used by features that require full low beam headlamp intensity such as low beam headlamp operation in manual, wiper activated headlamp (WAH), or auto modes (nominal: 100% duty cycle).
  • Off Mode: This is the default mode of the system that will occur when none of the features described above are active. The BCM will deactivate its PWM output (0% duty cycle) during this mode.

The normal battery voltage input to the HDM must be between 6 and 16 volts DC to operate. Any deviation to these values could cause improper operation.

Major components of this system are the BCM, HDM, ambient light sensor, multifunction switch, park brake switch and low beam headlamps.

The headlamps may be turned on in three different ways. First, when the driver places the headlamp switch in the HEADLAMP position, normal operation occurs. Second, with the headlamp switch is placed in the AUTO position, automatic lamp control (ALC) occurs. During ALC control, the headlamps will be in daytime running lamp (DRL) operation in daylight conditions, or low beam operation in low light conditions. Third, in wiper activated headlamp (WAH) mode. Only when the wiper system is activated while the vehicle is in gear, the wiper blades have completed at least 3 cycles, and then a 35 second time period expires, will the BCM switch from DRL mode to headlamp mode during daylight conditions. When the gearshift lever is placed in the PARK or NEUTRAL position or if the wipers are turned off, normal manual or ALC operation will resume after approximately 60 seconds.

The HDM and high beam relay receive battery positive voltage directly from the battery. The BCM supplies a 100% duty cycle PWM ground signal to the HDM for automatic headlight control and normal headlight operation. The BCM also supplies ground to the high beam relay coil for high beam headlight operation. When the driver places the headlamp switch in the HEADLAMP position and the dimmer switch is in the low beam position, the HDM switches to full output sending current flow through the left and right low beam headlamp fuses to both low beam headlamps. The dimmer switch sends a ground signal to the BCM in the high beam position and a momentary ground signal in the flash-to-Pass (FTP) position from G102 to deactivate the low beam headlights and activate the high beam headlights. With the headlights in the low beam position, the high beams may be momentarily turned on or flashed by activating the FTP portion of the switch.

The instrument panel cluster (IPC) illuminates the high beam indicator when the body control module (BCM) detects that the high beams are requested. The IPC receives a class 2 message from the BCM requesting illumination.

The Headlamps On at Exit and Perimeter Lighting modes can be adjusted using the steering wheel controls to select the desired fuction as displayed in the driver information center. The Headlamps On at Exit selection will allow the driver to customize the period of time that the headlamps remain illuminated upon exiting the vehicle. This period can be adjusted from 0 seconds to 180 seconds. The Perimeter Lighting feature allows the driver to select if they desire the headlamps and backup lamps to illuminate when the door UNLOCK button on the key fob is activated. This feature can be turned ON or OFF by using the driver information center steering wheel control buttons.

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

***** *****

Ask Your Own Chevy Question
Customer reply replied 2 years ago
Way above my level of understanding. Should I take to a mechanic?
Chevy Mechanic: Daniel Jones,
 replied 2 years ago

If you replaced the switch and they are intermittently working it might be difficult for you to try and figure it out. It would probably be better for you to take it to a mechanic.

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

***** *****

Ask Your Own Chevy Question
Chevy Mechanic: Daniel Jones,
 replied 2 years 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

***** *****

Ask Your Own Chevy Question
Was this answer helpful?
Ask Daniel Jones Your Own Question
Daniel Jones
Daniel Jones
Daniel Jones
Category: Chevy
Satisfied Customers: 506
506 Satisfied Customers
Experience: GM A Tech at Straub Buick GMC

Daniel Jones 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 was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money.

Todd LRochester NY

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

< Previous | Next >

Meet the Experts:

GM Tech (Cam)

GM Tech (Cam)

Chevy Technician

15,289 satisfied customers

GM Grand Master Technician 2007. 14 years experience.

Gary

Gary

Chevy Technician

9,357 satisfied customers

15 years GM master tech

Tim&#039;s Auto Repair

Tim's Auto Repair

mechanic

8,866 satisfied customers

Have owned a repair shop for 25 yrs.

Dave Nova

Dave Nova

Chevrolet Technician

7,092 satisfied customers

ASE Master Certification. GM World Class Certification

John

John

Master A.S.E Automotive technician

4,071 satisfied customers

A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician

Don - Mo Lurch

Don - Mo Lurch

Auto Mech / Electronics

2,918 satisfied customers

Chevrolet Cert., Heavy Line Mech, Race Shop Owner, Mobile Electronics.

Ron Z.

Ron Z.

- Chevy Tech -

2,734 satisfied customers

18+yrs experience. State Inspector and Chevy Diagnostics

< Previous | Next >

Related Chevy Questions
Wiring a 2003 Chevy mirror power for a 2000 Gmc. No
Wiring a 2003 Chevy mirror power for a 2000 Gmc JA: Okay, I'll connect you to the mechanic to discuss this further with you. Before I do, is there anything else you want him to know? Customer: No conn… read more
Dan
Dan
Automotive Technician
Vocational, Technical or Trade Scho
25 satisfied customers
2003 GMC 6.0 does not energize the starter. Neither no
2003 GMC 6.0 does not energize the starter JA: When you turn the key, do you get a single loud click, or a series of rapid ones? Customer: Neither no sound JA: What is the model of your '03 GMC? Custo… read more
AMEDEE
AMEDEE
AUTOMOTIVE TECHNICIAN
Vocational, Technical or Trade Scho
9,105 satisfied customers
I drive a 4 cyl 2011 chevy equinox and the P symbol that is
I drive a 4 cyl 2011 chevy equinox and the P symbol that is on when I park has started flashing when I drive … read more
GM Bob
GM Bob
Automobile Technician
High School or GED
1,035 satisfied customers
2007 chev hhr power steering assist light comes on & power
2007 chev hhr power steering assist light comes on & power steering is gone. Shut off car & start up steering is ok for awhile,time varies. Have replaced both applicable fuses,what now?… read more
HDGENE
HDGENE
Master Technician/Lead Technician
Associate Degree
2,835 satisfied customers
95 6.5 diesel. Engine won't start. Glow plug light, water in
95 6.5 diesel. Engine won't start. Glow plug light, water in fuel light. Throttle service light. Service engine light isn't coming on. … read more
eric remington
eric remington
FORMER SHOP OWNER/TECHNICIAN/INSPECTOR
associates degree
570 satisfied customers
2007 chevy malibu with 4 cylinder, goes into reduced power
2007 chevy malibu with 4 cylinder, goes into reduced power mode … read more
Dan
Dan
Automotive Technician
Vocational, Technical or Trade Scho
25 satisfied customers
05 silverado small evap leak, have renewed gas cap and purge
05 silverado small evap leak, have renewed gas cap and purge solenoid under hood … read more
Ron Z.
Ron Z.
- Chevy Tech -
Vocational, Technical or Trade Scho
2,734 satisfied customers
Working on a 2011 freightliner sprinter 3500 with a 3.0 L
Working on a 2011 freightliner sprinter 3500 with a 3.0 L diesel engine automatic transmission. We're looking for the transmission fluid type. Thank you… read more
fordguy4u
fordguy4u
Automotive Tech
Vocational, Technical or Trade Scho
70 satisfied customers
I have a 2003 silverado 2500 hd and i have a p0300 random
i have a 2003 silverado 2500 hd and i have a p0300 random misfire code. Before i thought it was related to a code i was getting for o2 sensor. i replaced the o2 sensor but still have the p0300 code. o… read more
Gary
Gary
Chevy Technician
Vocational, Technical or Trade Scho
9,357 satisfied customers
I have a 2011 cjevy cruze lt. My air bag module is not
I have a 2011 cjevy cruze lt. My air bag module is not communicating have tried new module same result. Checked fuses and ok. Looked for for fuses in bcm but did not see any… read more
roy
roy
Associate Degree
3 satisfied customers
My 2012 Chevrolet Malibu keeps shutting down, I replaced a
My 2012 Chevrolet Malibu keeps shutting down, I replaced a camshaft sensor, ignition coil packs, tune-up spark plug, belt tensioner, and map sensor. What could be causing it to shut down when ever I'm… read more
rpmdiag
rpmdiag
High school
7,589 satisfied customers
I am having an issue where when I am at a stop light getting
Hello, I am having an issue where when I am at a stop light getting ready to accerlerate to go forward or green or when I am at a yield or in a turning lane, my car will stop accelerating, the brake w… read more
HondaPlatinum
HondaPlatinum
High School or GED
148 satisfied customers
Can I put a clutch master cylinder for a 92 GMC on a 91 GMC?
Can I put a clutch master cylinder for a 92 GMC on a 91 GMC? … read more
Expert-Repair
Expert-Repair
Owner Kingsland Auto & Marine Services
Vocational, Technical or Trade Scho
11 satisfied customers
No gas gage. 2004 Chevy Silverado 1500. My self
No gas gage JA: Has the vehicle turned into a gas hog? And how does it start -- same as usual? Customer: Yes JA: What is the model/year of your Chevy? Customer: 2004 Chevy Silverado 1500 JA: Are you f… read more
Gary
Gary
Chevy Technician
Vocational, Technical or Trade Scho
9,357 satisfied customers
I have a 2001 Chevy Cavalier LS /2.2...My issue is...A
I have a 2001 Chevy Cavalier LS /2.2...My issue is...A wining sound when Reving the gas.. In park and while driving.. What is the Problem??? … read more
AMEDEE
AMEDEE
AUTOMOTIVE TECHNICIAN
Vocational, Technical or Trade Scho
9,105 satisfied customers
I Would Like to get a Vin Build Sheet for my new 2017
I Would Like to get a Vin Build Sheet for my new 2017 Silverado … read more
GM Bob
GM Bob
Automobile Technician
High School or GED
1,035 satisfied customers
I have a 2010 Chevy Colorado that intermittently runs rough
I have a 2010 Chevy Colorado that intermittently runs rough and stalls out when idling at a red light or stop sign. About six months ago I had a rebuilt engine (Vortec 3700 I5) put in it and the mecha… read more
Mechanic01
Mechanic01
2,586 satisfied customers
I have a 1997 chevy 1500 silerado no crank no start no power
I have a 1997 chevy 1500 silerado no crank no start no power to dash,horn,or lights good starter good battery no lights come on when key is turned on … read more
AMEDEE
AMEDEE
AUTOMOTIVE TECHNICIAN
Vocational, Technical or Trade Scho
9,105 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