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Low beams not working

Tiny
SEALNUMBR4
  • MEMBER
  • 2004 CHEVROLET TRAILBLAZER
  • 4.2L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 220,000 MILES
I replaced both fuses, the HDM relay, the headlight switch and checked both bulbs to no avail. All other lights work including parking and high beams. What else could be the issue?
Wednesday, July 31st, 2019 AT 8:48 PM

22 Replies

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

What fuses did you replace and where was the location of them in your vehicle?

Thanks,
Alex
2CarPros
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Friday, August 2nd, 2019 AT 3:31 AM
Tiny
SEALNUMBR4
  • MEMBER
  • 7 POSTS
I replaced the left and right low beam fuses on the fuse panel under the hood.
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Friday, August 2nd, 2019 AT 11:31 AM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello again,

Did you check Fuse #53(15A) HDM in the Under hood Fuse Box. This Fuse feeds the power side of the Headlight Driver Module Relay then it splits into a parallel circuit feeding the left and right headlights, then each sides headlights are fused again. I have included a headlight circuit wiring diagram for you as well as a diagram and callout for the Under hood Fuse Box for your vehicle in the diagrams down below for reference. Please get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
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Friday, August 2nd, 2019 AT 8:33 PM
Tiny
SEALNUMBR4
  • MEMBER
  • 7 POSTS
I swapped that fuse out and still nothing. I checked voltage at the plug and I am getting 12.1v. I unplug the bulb and replug it in with the switch in the on position, and the bulb flashes on for 0.5 seconds.
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Saturday, August 3rd, 2019 AT 5:18 PM
Tiny
SCGRANTURISMO
  • MECHANIC
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Hello again,

Please check Ground #106 on the lower left side of the engine. This is the ground for the HDM relay control side, which is the electromagnet that when energized pulls the switch closed and allows current to flow to the headlights. Unwanted resistance here would cause current not to flow to the lowbeam headlights. In the diagrams down below I have included directions for Ground Inspection. Please go through them and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
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Sunday, August 4th, 2019 AT 5:04 AM
Tiny
SEALNUMBR4
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  • 7 POSTS
I couldn't find where that ground bolted to the engine, so I ran a new ground for the relay instead. With the new ground the headlights still do not turn on.
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Saturday, August 10th, 2019 AT 12:04 PM
Tiny
SEALNUMBR4
  • MEMBER
  • 7 POSTS
I couldn't find where that ground bolted to the engine, so I ran a new ground for the relay instead. With the new ground the headlights still do not turn on.
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Saturday, August 10th, 2019 AT 12:04 PM
Tiny
SCGRANTURISMO
  • MECHANIC
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Hello again,

Okay, so you have 12.1 volts at both the left and right headlights connectors where the bulb plugs into with the headlight switch on for the low beam headlights?

Thanks,
Alex
2CarPros
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Saturday, August 10th, 2019 AT 5:23 PM
Tiny
SEALNUMBR4
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I only tried at the drivers side light, but seeing as they went out simultaneously I assume I will get the same result on passenger side.
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Saturday, August 10th, 2019 AT 6:23 PM
Tiny
SCGRANTURISMO
  • MECHANIC
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Hello again,

Could you please verify if you have battery voltage at both the left and right headlight bulb connectors with the headlight switch on for low beams. Also I was able to find this Technical Service Bulletin (TSB) that may or may not have bearing on what is going on with your vehicle. I have included it in the diagrams down below for you.

Thanks,
Alex
2CarPros
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Sunday, August 11th, 2019 AT 3:02 AM
Tiny
SEALNUMBR4
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It is getting 12.2v at the passenger connector. The lights are not flickering, they are not coming on whatsoever.
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Sunday, August 18th, 2019 AT 11:41 AM
Tiny
SCGRANTURISMO
  • MECHANIC
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Hello again,

Okay, let's start from the beginning. In the diagrams down below I have included a factory diagnostic troubleshooting guide for your headlamps. Please go through this guide and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
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Sunday, August 18th, 2019 AT 12:14 PM
Tiny
JHC3
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TRAILBLAZER
Electrical problem
2004 Chevy Trailblazer 6 cyl Four Wheel Drive Automatic

My low beam lights are not working. It's not the fuse or the bulbs. What else should I check?
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Monday, January 4th, 2021 AT 1:26 PM (Merged)
Tiny
QUESTIONS32
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  • 10 POSTS
I am having the same problem right now with my 2005 Trailblazer. I got a new relay fixed it
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Monday, January 4th, 2021 AT 1:26 PM (Merged)
Tiny
DARTHMILL1
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 89,500 MILES
Both of my low beams quit working. The fuses are fine and I replaced the bulbs. Also, it seams my high beams either quit working as well or they won't come on during the day. I have the daytime running lights.
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Monday, January 4th, 2021 AT 1:26 PM (Merged)
Tiny
HMAC300
  • MECHANIC
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There is a headlight relay in the under hood fuse box. Your bright lights will only work when you put them on via your high beam switch.
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Monday, January 4th, 2021 AT 1:26 PM (Merged)
Tiny
PRECOCIOUSKAREN
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
My regular headlamps keep going out. I have replaced the bulbs and the fuses are ok and the relays checkout. What else can I do myself to get them working again. I had a brake job 3 weeks ago and that is when the problem began.
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Monday, January 4th, 2021 AT 1:26 PM (Merged)
Tiny
JDL
  • MECHANIC
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Welcome to the forum. Any fuses that you checked, did you use a testlite to check that the fuse circuit has voltage when it should? Also, at the relay/s, I'd have to check the voltage circuits, with a testlite. With the low beam relay, voltage to the load side of relay is hot all the time. The bcm sends voltage to the coil side of relay in order to energize. The ground for the coil is constant.
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Monday, January 4th, 2021 AT 1:26 PM (Merged)
Tiny
MIDNITE49
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 79,000 MILES
My low beam headlamps are not working. I have replaced the bulbs, checked the fuses and they are ok. The photo sensor on the dash is working because it turns all the other lights on. The overide switch on the instrument cluster seems to be working. The high beams are working and the fog lamps are working. All the lights on the vehicle work except the low beam lights. Is there some type of relay that I might need to check?
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Monday, January 4th, 2021 AT 1:26 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Welcome to the forum, did you use a testlite on the fuse circuit, to see if circuit is hot? My info shows different fuses for left and right low beams. The fuses are in the underhood fuse box. Also, there is a headlamp driver module relay in the underhood fuse box, I believe that is for low beams. Check voltage to load side of relay and to the coil side of relay. Voltage to the coil side of relay, may not be 12 volts, use a digital multimeter to check.
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Monday, January 4th, 2021 AT 1:26 PM (Merged)

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