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?
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Wednesday, July 31st, 2019 AT 8:48 PM

12 Replies

Tiny
SCGRANTURISMO
  • EXPERT
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
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
  • EXPERT
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
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
  • EXPERT
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
  • MEMBER
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
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
  • EXPERT
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
  • MEMBER
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
  • EXPERT
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
  • MEMBER
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
  • EXPERT
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

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