Buick 2007 LaCrosse Low Beam headlamps won't work

Headlamps
You can use the headlamps two different ways.
• Place the headlamp switch in the HEAD position for normal operations
• Place the headlamp switch in the OFF position for automatic lamp control (ALC) operation. During ALC the low beam headlamps are ON for daytime running lamp (DRL) operation in daylight conditions at reduced intensity or low beam headlamps ON at full intensity with exterior park lamps ON in low light conditions.
The body control module (BCM) applies a pulse width modulated (PWM) voltage to the headlamp module and high beam relay in the underhood fuse block. The ground for the headlamp module is supplied from G113 or G115. For normal manual low beam operation when the headlamp switch is place in the HEAD position, ground from G202 is applied through the headlamp switch and to the BCM through the headlamp switch headlamps ON signal circuit. The BCM then applies a PWM voltage to the headlamp module/high beam relay voltage supply circuit. The headlamp module then applies battery positive voltage through the left front (LF) and right front (RF) LO Beam fuses to the left and right low beam headlamps. The ground for the left headlamps is supplied by G101 and the ground for the right headlamp is supplied by G100.
For high beam operation, ground is applied at all times to the headlamp dimmer switch from G202. When the headlamp dimmer switch is placed in the HIGH position, ground is then applied through the headlamp dimmer switch signal circuit to the BCM. The BCM then applies a ground to the headlamp high beam relay control circuit. This energizes the HI Beam relay, the relay then applies battery positive voltage through the LF and RF HI BEAM fuses to the LF and RF high beam headlamps. The ground for the left headlamps is supplied by G101 and the ground for the right headlamp is supplied by G100.
The BCM then sends a class 2 message to the instrument cluster in order to illuminate the high beam indicator lamp. If the headlamp switch is left in the HEAD position, the inadvertent power control feature will turn OFF the headlamps after 10 minutes after you turn the ignition switch to the OFF position. If you place the headlamp switch in the head position after the ignition switch has been turned OFF, or if the ignition switch is in ACCY position, the headlamps will remain ON until you turn them OFF or until the battery runs dead.

This is usually caused by a failed front control module as this unit controls the lighting on the vehicle!
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High beam switch moat likely, have you checked relays and fuses?

Headlight module ! You can get one at a buick dealer for about 40 buck. Good luck!

The high and low beam lights use the same power source, so if the low beams work the high beams have power.
There is a low and high beam relay controlled by the dimmer switch.
If the low beams work and the high beams don't, and the bulbs are good, check the dimmer switch and the high beam relay.

You have a bad electrical connection. Check the wiring harness and both sides of it's connectors for corrosion and or breakage. The connector terminals will become worn and corroded and the wiring sheaths a prone to weathering and become brittle. Replace or clean as needed.

your low beam bulbs are bad they go for about 21.00 dollars for a pack of two

The relay under the hood may have gone out. We had the same problem on our 2007 Buick LaCrosse CX. The bulbs were fine, high beams worked, all turn signals and everything except the low beams turned on. Turns out the relay had gone bad.

For Audi A4 the fuse box is located on the left side of dashboard behind a plastic cover (for left hand steering wheel vehicle). On inner face of the plastic cover you will find the fuse diagram.
First fuse on first row from left upper corner is Fuse Nr.20 = F20 (15A) - RH headlamp low beam, headlamp adjustment.
First fuse on second row from left upper corner is Fuse Nr.21 = F21 (15A) - LH headlamp low beam, headlamp adjustment.

do your flash to pass lamps light when you pull the stalk towards you? If yes, the bulbs are ok.
Do the hig beams work?
Your headlamps have sepaerate fuses for each headlamp and you have a low beam relay and a high beam relay under the hood in the black box.
If everything is out, I suspect a bad headlamp switch.
Check car-part.com and look on page with * for cheapest price.

Your owner manual will identify fuses & relays.

PS, You did not recently instal high current bulbs did you? If yes, put originals back in.

HEADLAMPS

The voltage is supplied to the lamp switch through a fuse. This fuse is located in the central junction box in the left-hand footwell.
When the headlamps are switched on, a voltage is supplied to the high beam/low beam switch and to the low beam relay. The relay for the low beam is located in the battery junction box (BJB) in the engine compartment.
If the high beam/low beam switch is set to "low beam", then a voltage is supplied through the low beam relay to the low beam part of the headlamp assembly. The left and right-hand low beams are fused separately. The fuses are located in the battery junction box (BJB) in the engine compartment.
If the high beam/low beam switch is set to "high beam", then a voltage is supplied through the high beam relay to the high beam part of the headlamp assembly. The left and right-hand high beams are fused separately. The fuses are located in the battery junction box (BJB) in the engine compartment.

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Lamp Switch
Removal

1. CAUTION: Disconnect the battery ground cable. For additional information, refer to Section 414-01 .
   Remove the lower driver's side footwell trim.

1. Detach the lamp switch bezel.
   • Remove two screws.

1. Remove the light switch.
   • Remove three screws.
• Disconnect the electrical connector