Headlights don't work 2002 TB - Page 2 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 5.3L V8 Engine and Drivetrain > OEM Issues

OEM Issues Original Equipment Repairs and/or Problems

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  #11  
Old 01-21-2019, 11:10 AM
1988scotsdale 1988scotsdale is offline
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2002 Chevy TrailBlazer LT EXT
Majestic Red Metallic 4.2L I6 2WD
Join Date: Sep 2011
Location: Chesapeake, A
Posts: 12
"Thanks, EnvoyBoy2004, While using the following link, https://www.youtube.com/watch?v=QgPfUrkliUg&t=53s, I have completed all test. slot 2 is a positive voltage, slot 6 is ground, slot 4 can power the headlights, but slot 5 indicates no voltage when the headlights are turned on. Furthermore, I have replaced the headlight switch with no change, plus I have checked all fuses for continuity and the headlight relay 46. In my ignorance, I assumed I am not getting a ground thru slot 5. Thanks again"

Thanks all who have replied.
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  #12  
Old 01-21-2019, 03:47 PM
EnvoyBoy2004's Avatar
EnvoyBoy2004 EnvoyBoy2004 is offline
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2004 GMC Envoy SLT
Graphite Metallic 4.2L I6 4X4
Join Date: Sep 2014
Location: NY
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The BCM (Body Control Module) controls the low beam function. There are 2 functions, one is full on brightness and the other is DRL (Daytime Running Lights). For the DRL function, the BCM provides a pulsewidth grounding signal to pin 5 of the Relay #46. This turns the low beams on at 80% brightness. For the full on (night-time) brightness I am uncertain of the signal provided to pin 5. Checking pin 5 with a DVM (Digital Volt Meter) in the DRL mode will not show a reading because the signal is changing rapidly.

Have you tried moving the headlight switch on the dash to the full on headlight position to see if the low beams turn on? If they do, then there is a problem with either the BCM or the light sensor on the top center of the dash.
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  #13  
Old 01-21-2019, 05:24 PM
1988scotsdale 1988scotsdale is offline
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2002 Chevy TrailBlazer LT EXT
Majestic Red Metallic 4.2L I6 2WD
Join Date: Sep 2011
Location: Chesapeake, A
Posts: 12
Thanks for your info. I used a trouble light between POS post and slot 5#, turn the headlights on and the trouble light did not illuminate. I install a new headlight switch with no change. I assumed a problem with a ground. To change the light sensor seems a lot of disassembly.
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  #14  
Old 02-17-2019, 12:59 PM
1988scotsdale 1988scotsdale is offline
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2002 Chevy TrailBlazer LT EXT
Majestic Red Metallic 4.2L I6 2WD
Join Date: Sep 2011
Location: Chesapeake, A
Posts: 12
Thanks Much! It was the light sensor. I'll get it inspected and back on the road this week.
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