All other lights work fine. Checked the fuses, replaced the HDM relay, replaced both the bulbs, Replaced one of the headlight connectors even though neither one showed any signs of wear or damage or melting but they still won't come on.
I'm not sure what else to try. ??????/ Try looking at a wiring diagram an using a DVOM - digital volt ohmmeter an test the electrical circuits , rather then just replacing parts . If you don't know how to test , suggest you take it to a qualified repair shop. Test for B+ - battery positive voltage at the HDM relay an for control from the BCM . Checking for codes in the BCM would also be a good idea.
DTC B2575 Headlamp Control Circuit
When the body control module (BCM) senses a request for headlamp or daytime running lamp (DRL) illumination, the BCM sends a pulse width modulated (PWM) ground signal to the low beam headlamp driver module through the low beam headlamp driver module control circuit. The low beam headlamp driver module will illuminate the headlamps, adjusting the intensity based on the PWM signal received.
Free wiring diagrams here http://www.bbbind.com/free-tsb/ Enter vehicle info. Year , make , model an engine size. Under system click on lighting , then under subsystem click on headlamps . Click the search button then the blue links one at a time .
https://www.youtube.com/watch?v=SO-eKuhCOqc&t=125s
Do you know how relays work ?
https://www.youtube.com/watch?v=Gg20X-FwGzg&t=183s
Thanks!
I park in a parking garage for work and when I enter and it’s dark, I hear a click and my park lights come on and the little green light at the switch inside the car comes on like my automatic lights have come on but just the yellow park lights come on, not the low beams so I have no clue.
Have the BCM checked for codes , not the OBD engine computer . This is a problem for a professional automotive technician , buying a manual won't help if you don't know how to use it or knowing how to test automotive electronics , part stores are just that , they have no clue of automotive electronics testing , they have no scanner to test body computers .
Could be the sensor on top of the dash , lets the computer know if it's dark or light out side . Will the low beams come on if you manually turn on the lights ? So , they don't work in auto position ?
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 and the park brake switch as inputs. In general, the HDM will operate in 1 of 3 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: 85% 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 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 low beams won't come on in any condition. I can't manually switch them on or anything. I have a friend who is going to come over this weekend and look at it because he has way more experience than I do and he said he was going to check to see if it pulled any codes. I'll let him know what you said about the BCM. Thanks so much for all of the advise!
Good luck . Have him also check for battery voltage at the HDM relay an for BCM control . Videos on how to check this on youtube. https://www.youtube.com/watch?v=Gg20X-Fw...
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Cud b flaw in harness wiring from age or vibration. Mite hava module issue. Swingit into a partstore..freehelp
thanks!
Part stores sell parts , don't know how to trouble shoot electrical problems
Depends on store and employees workn there..i there..if they wanna sell it makes sence
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Headlight switch
thanks!
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Get the help from service and repair manual with diagram to locate and fix the problem on your own and you will get the manual from the given link https://toolsnyou.com/Brands/gmc-vehicle-service-manuals/
SOURCE: Both low beam headlights on my 05 GMC envoy do not
Check your headlamp relays under the hood, should be located on either the L/H or R/H fender well , could be inside a black plastic box labled fuses and relays... there will be a label on the underside of the lid to this box locate the relays as per lables... please rate my help thanks...
SOURCE: 2006 GMC Envoy low beam
Hello, try to start by checking the headlight relay and headlight fuse. You
also may want to check to make sure the bulbs aren't blown out. If those
parts check out to be fine and in working order, you may need to
replace the turn signal assembly in the steering column. This part
controls the hi/low beams. This may sound crazy but, when GM wired
their older trucks, they wired the headlights to go from the battery,
to the hi/low beam switch, then to the headlight switch (to the left of
the steering wheel) then out to the light bulbs. You can kind of test
to see if this part is good by making a fist and (with your headlights
on) gently hitting the plastic cover for your steering column that is
right behind your actual steering wheel. This could cause your
headlights to flicker on and off.
Thanks
SOURCE: 2003 gmc Envoy Low Beam Headlights both quit at
Relay in fuse box under hood on driver side wheel well labeled HDM, #46 on 2004 Envoy XUV. Swap with relay #45 labeled "Fan" to test. That was my problem.
Good Luck,
Sam
SOURCE: 2002 Acura TL low beam headlight
How to Shift my headlight beam from position.
from I replace my headlight it's spatting directly on the ground..What can i do to change it from position
SOURCE: My 2003 GMC Yukon XL Denali low beam headlights do
The problem is likely your multi purpose signal light switch. If you take the lever and move it from hi to low beam will the low beams come on? It is common for this multi purpose (real expensive ) switch to fail after a period of time! The steering wheel may have to be removed, to change it. The air bags will also need to be disabled so as not to active them while removing the switch.
?€¢
Full Intensity Mode: This mode is used by features that require full low beam headlamp intensity such as low beam headlamp operation in manual 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.
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Usually answered in minutes!
Headlamps Inoperative - Low Beams
Step
Action
Yes
No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference: Lighting Systems Connector End Views or Data Communication Connector End Views
1
Did you perform the Diagnostic System Check - Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle
2
Verify that the low beam headlamps are inoperative.
Do the low beam headlamps operate normally?
Go to Testing for Intermittent Conditions and Poor Connections
Go to Step 3
3
Is only one low beam headlamp inoperative?
Go to Step 4
Go to Step 5
4
Inspect the inoperative bulb for an open filament and connector for poor terminal contact and replace/repair as necessary. Refer to Headlamp Bulb Replacement or Wiring Repairs .
If no problem is found, repair the open, high resistance or short to ground in the low beam headlamp supply voltage circuit or ground circuit to the inoperative lamp. Refer to Circuit Testing and Wiring Repairs .
Did you complete the repair?
Go to Step 14
--
5
Test the headlamp switch signal and ground circuits for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct a condition?
Go to Step 14
Go to Step 6
6
Place the headlamp switch in the HEAD position.
Connect a fused jumper from ground to the headlamp switch signal terminal of the headlamp switch connector.
Do the low beam headlamps illuminate?
Go to Step 9
Go to Step 7
7
Connect a fused jumper from ground to the headlamp driver module control circuit terminal at the headlamp driver module (HDM) in the underhood fuse block.
Do the low beam headlamps illuminate?
Go to Step 10
Go to Step 8
8
Test the headlamp driver module ground circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct a condition?
Go to Step 14
Go to Step 12
9
Inspect for poor connections at the harness connector of the headlamp switch. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?
Go to Step 14
Go to Step 13
10
Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?
Go to Step 14
Go to Step 11
11
Replace the BCM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?
Go to Step 14
--
12
Replace the HDM. Refer to Relay Replacement .
Did you complete the repair?
Go to Step 14
--
13
Replace the headlamp switch. Refer to Headlamp Switch Replacement .
Did you complete the repair?
Go to Step 14
--
14
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 3
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