You very well could have a couple of faulty relays 45 & 46 in the underhood fuse / relay box . Could also have DTC'S - diagnostic trouble code's stored in the BCM - body control module .
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.
DTC B2585 Park Lamp Control Circuit
When the body control module (BCM) receives a ground signal from the headlamp switch commanding to illuminate the park lamps, the BCM will energize the park lamp relay by grounding the park lamp relay control circuit.
DTC B3802 Park Lamps Request Circuit
The body control module (BCM) monitors the park lamp switch signal circuit and the headlamp switch headlamps on signal circuit in order to determine when the park lamps and headlamps should be illuminated. When the headlamp switch is turned to PARK, the BCM senses that the park lamp switch signal circuit is grounded and the headlamps switch headlamps on signal circuit is open. The BCM will then energize the park lamp relay illuminating the park lamps. When the headlamp switch is turned to HEAD, the BCM senses that the park lamp switch signal circuit and the headlamp switch headlamps on signal circuit are grounded. The BCM will then energize the park lamp relay and headlamp driver module (HDM) illuminating the park lamps and headlamps.
relay # 46 is the HDM headlamp driver module .
SOURCE: 2003 GMC Envoy Low beam headlights will not work.
I would start by checking the headlight relay and headlight fuse. You also may wanna 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. It's not 100% guarenteed that this method will work, but it may.
Any questions, just ask!
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: the auto headlights on my
Relay #46 in the underhood fuse panel is probably bad. You can verify this by swapping it with relay #45. Also, sometimes the relay contacts become corroded, check these when you have the relay out.
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