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Headlights don't work 2002 TB

3K views 13 replies 6 participants last post by  1988scotsdale 
#1 ·
My low beams will not illuminate. The high beams will come on if I hold the turn signal back to flash them. I have checked the fuses and relays under the hood. would someone tell me where the grounds are for the lights? Thanks much.
 
#3 ·
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.
 
#4 ·
Have you tried swapping #45 & 46? These are not actually relays, they are electronic modules that produce a Pulse Width Modulation output based on a variable signal from the PCM.

Don't over think this. The "relay" is a common failure part, and make sure to get an OEM part or a name brand.
 
#5 ·
Headlight relays have been swapped and replaced. Note I am not passing voltage thru slot 5...the control. As per the troubleshooting method, I mentioned, I should have gotten an indication of voltage when I turned the headlight on. I am using a voltage indicator light to test with.
 
#10 ·
I've seen issues with the relays on these, AND the actual headlight switch. The relay is a quick and easy test as others have mentioned by swapping it with another in the fuse box. As far as the headlight switch, grab another from a junk yard for cheap if you can, they're actually very easy to replace. Pull off the cover on the side of the dash, reach in and there's 4 clips that hold it in. While pushing in on the switch from the outside, you can reach in through that opening in the dash with the side panel removed and pop those 4 clips loose and the light will basically fall into the dash. Fish the switch assembly out through that side opening and unplug it. Then plug in the new switch and test it out before putting it back in. If everything works again, reassembly is just the revers of removal. The switch just pops right back into place.

But I would agree that 9 times out of 10, it's the relay. I personally know 2 people that have had the relay issue, a buddy at work with his Envoy and a friend with an Ascender. But my father had an Ascender that the headlight switch failed on and caused the same thing, no low beams, so it does seem to be an issue with them, although not as common as the relay.

Just another path to chase if the relay doesn't fix it :)
 
#11 ·
"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.
 
#12 ·
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.
 
#13 ·
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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