I can't get the white light on trailblazer headlamp to activate

wow no year car told,why? 1998 to now, is it USA? car?
yes sold in S.America too, 2011 and up.
the outside casing lens?
the service manual covers this only
no problem told at all just how to. ( so I guess the whole thing out and in)
why skip saying the problem first.? to the blind.
is the front of the light casing all ugly and yellow?
2001-2008 (separate model, North America)
so I guess 2003, ( using ESP and Karnac mind meld)

replacing all this.??????

https://www.rockauto.com/en/catalog/chevrolet,2003,trailblazer,4.2l+l6,1412277,body+&+lamp+assembly,headlamp+assembly,10762

PULL steps

Headlamp Replacement (TrailBlazer) Removal Procedure

1. Open and support the hood.
2. Remove the grille. Refer to ' Grille Replacement (Chevrolet).
3. Use a flat-bladed tool in order to release the clips that retain the grille to the headlamp panel.
4. Remove the grille from the vehicle.
5. Pull up on the retaining tabs?(1) in order to remove the headlamp assembly from the headlamp panel.
6. Disconnect the headlamp leveling electrical connector from the motor/actuator if equipped.
7. Disconnect the headlamp electrical connector?(2) from the headlamp assembly.
8. Remove the side marker socket?(4) from the headlamp assembly.
9. Remove the park/turn socket?(3) from the headlamp assembly.
10. Remove the headlamp assembly from the headlamp panel.

if confused buy the service manual
or get the car serviced in real shop.

Low beam's don't work , how about high beams . Low beam relay is turned on by the BCM - body control module , headlamp switch is a input to the BCM . Your best bet mite be to take it to a qualified repair shop , rather then guessing an replacing parts you don't need . Hooking up a scan tool an checking for DTC'S - diagnostic trouble codes should have been the first step before replacing parts .
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 , wiper motor, and the park brake switch as inputs. In general, the HDM will operate in one of three 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: 81% 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, wiper activated headlamp (WAH), 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.

Chevy Trailblazer headlights don work HDM input output testing YouTube

The Headlamps On at Exit and Perimeter Lighting modes can be adjusted using the steering wheel controls to select the wanted function as displayed in the driver information center. The Headlamps On at Exit selection will allow the driver to customize the period of time that the headlamps remain illuminated upon exiting the vehicle. This period can be adjusted from 0 seconds to 180 seconds. The Perimeter Lighting feature allows the driver to select if they want the headlamps and backup lamps to illuminate when the door UNLOCK button on the key fob is activated. This feature can be turned ON or OFF by using the driver information center steering wheel control buttons.
programming Features with the Driver Information Center (DIC)
To enter programming with the driver information center (DIC), perform the following actions:
Turn the ignition to RUN.
Place the vehicle in PARK.
Press the Personalization button on the steering wheel to enter personalization programming.
Automatic Door Locks
Continue with the following steps in order to personalize the automatic door locks:
Press the Select button in order to enter the menu. The first choice seen is the current setting.
Press the Select button in order to scroll through the following options:
• LOCK DOORS: IN GEAR
• LOCK DOORS: WITH SPEED
Press the Personalization button in order to advance to the next option.
Press the Select button in order to enter the menu. The first choice seen is the current setting.
Press the Select button in order to scroll through the following options:
• UNLOCK DRIVER: IN PARK
• UNLOCK DOORS: IN PARK
• UNLOCK DOORS: AT KEY OUT
• UNLOCK DOORS: MANUALLY
Press the Personalization button in order to advance to the next option.
Remote Activation Verification
Continue with the following steps in order to personalize the remote activation verification feature:
Press the Select button in order to enter the menu. The first choice seen is the current setting.
Press the Select button in order to scroll through the following options:
• LOCK FEEDBACK: BOTH
• LOCK FEEDBACK: OFF
• LOCK FEEDBACK: HORN
• LOCK FEEDBACK: LAMPS
Press the Personalization button in order to advance to the next option.
Press the Select button in order to enter the menu. The first choice seen is the current setting.
Press the Select button in order to scroll through the following options:
• UNLOCK FEEDBACK: BOTH
• UNLOCK FEEDBACK: OFF
• UNLOCK FEEDBACK: HORN
• UNLOCK FEEDBACK: LAMPS
Press the Personalization button in order to advance to the next option.
Delayed Lighting
Continue with the following steps in order to personalize the delayed lighting feature:
Press the Select button in order to enter the menu. The first choice seen is the current setting.
Press the Select button in order to scroll through the following options:
• HEADLAMP DELAY: 10 SEC
• HEADLAMP DELAY: 20 SEC
• HEADLAMP DELAY: 40 SEC
• HEADLAMP DELAY: 1 MIN
• HEADLAMP DELAY: 2 MIN
• HEADLAMP DELAY: 3 MIN
• HEADLAMP DELAY: OFF
Press the Personalization button in order to advance to the next option.
Perimeter Lighting
Continue with the following steps in order to personalize the perimeter lighting:
Press the Select button in order to enter the menu. The first choice seen is the current setting.
Press the Select button in order to scroll through the following options:
• PERIMETER LIGHTS: OFF
• PERIMETER LIGHTS: ON
Press the Personalization button in order to advance to the next option.

has the light got wet somehow?

Try not to touch the buld as you do the installation. There is a access cover in the back of the head lamp. This gives you access to the headlamp. Now when you get to the light buld and socket turn counterclockwise.Then the light bulb wil come out of its socket.From here disconnect the electrical connection.Now for the installation connect the electrical socket to the headlamp bulb.Install the buld in the socket,by rotating socket clockwise locking the retaining tabs to the housing,install cover test the light and you are done

Headlamp Removal & Installation Bulb Replacement To Remove:
CAUTION
Halogen bulbs contain pressurized gas. Mishandling a bulb may result in the bulb shattering into flying glass fragments.
CAUTION
Make sure to wear eye protection when handling a halogen bulb.
CAUTION
Do not touch the glass of a halogen bulb, only handle the bulb by the base.
CAUTION
Do not allow a halogen bulb to come into contact with dirt or moisture.
CAUTION
Make sure to dispose of a used halogen bulb properly.
CAUTION
Do not allow children to handle halogen bulbs.

1. Turn the lamp switch to the off position.
2. Make sure the bulb is cool before changing.
3. Remove the headlamp assembly from the headlamp panel.
4. Remove the rear access cover from the headlamp assembly.
5. Disconnect the headlamp connector.
6. Remove the bulb from the headlamp assembly by rotating the bulb and socket counterclockwise.

To Install:

1. Connect the headlamp connector.
2. Install the bulb into the headlamp assembly by rotating the bulb and socket clockwise.
3. Install the rear access cover onto the headlamp assembly.
4. Install the headlamp assembly into the headlamp panel.

Headlamp Assembly Chevrolet To Remove:
Headlamp Assembly (Chevrolet)

1. Remove the grille from the front of the vehicle.
2. Release the headlamp assembly retaining tabs.
3. If equipped, disconnect the headlamp leveling motor connector.
4. Disconnect the headlamp connector.
5. Remove the park/turn and side marker bulb sockets from the headlamp assembly.
6. Remove the headlamp assembly from the headlamp panel.

To Install:

1. Place the headlamp assembly into the headlamp panel.
2. Install the park/turn and side marker bulb sockets into the headlamp assembly.
3. Connect the headlamp connector.
4. If equipped, connect the headlamp leveling motor connector.
5. Lock the headlamp assembly retaining tabs.
6. Install the grille onto the front of the vehicle.

the center section of your grill will pop off. you can use a small pry bar to help but be careful plastic will brake easy. the headlamp is held in with two blastic bars, that slide up to release. they are white and the ends are located at the top rear of the lamp. the wire is very short to the turn bulb so it must be disconnected to access the high and low beam.

Headlamp Removal & Installation Bulb Replacement To Remove:
CAUTION
Halogen bulbs contain pressurized gas. Mishandling a bulb may result in the bulb shattering into flying glass fragments.
CAUTION
Make sure to wear eye protection when handling a halogen bulb.
CAUTION
Do not touch the glass of a halogen bulb, only handle the bulb by the base.
CAUTION
Do not allow a halogen bulb to come into contact with dirt or moisture.
CAUTION
Make sure to dispose of a used halogen bulb properly.
CAUTION
Do not allow children to handle halogen bulbs.

1. Turn the lamp switch to the off position.
2. Make sure the bulb is cool before changing.
3. Remove the headlamp assembly from the headlamp panel.
4. Remove the rear access cover from the headlamp assembly.
5. Disconnect the headlamp connector.
6. Remove the bulb from the headlamp assembly by rotating the bulb and socket counterclockwise.

To Install:

1. Connect the headlamp connector.
2. Install the bulb into the headlamp assembly by rotating the bulb and socket clockwise.
3. Install the rear access cover onto the headlamp assembly.
4. Install the headlamp assembly into the headlamp panel.

on a 2003 Chevy Trailblazer, you have to remove the grill to access the back of the head lights. It takes a good pull (don't be afraid to use a little force). Pop the hood and there 4 metal pieces that slide up and several plastic pieces that pop up. You will see the lips on the metal slides (about an inch in width) and you pull those up to loosen the grill. There are 2 of these slides (one on each far side, almost hidden) that are hard to get your hand into that you might need a screwdriver or something for leverage to slide them up. Then pop up the plastic pieces holding the headlamps in place and with a little force pull the grill off.
Then you can access the back side of the headlamps to replace the bulbs.

The headlamps are in manual mode. you must change in the computer the option of the headlights to automatic and then check the manual control of the lights that should be in the complete left position with the orange light on.