Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1401 (LIGHTING SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL OUTPUT CONTROLS
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Scan Tool Output Controls
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Scan Tool Output Controls
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
Body Control Module (BCM) Scan Tool Output Controls
| Scan Tool Output Control | Additional Menu Selection(s) | Description |
|---|---|---|
| Light Test | Daytime Running Lamps | The BCM reduces the 100 percent pulse width modulated (PWM) headlamp driver module (HDM) control signal to a 85 percent duty cycle when there is sufficient light to the ambient light sensor and you select ON. The daytime running lights will remain illuminated until commanded OFF. |
| Light Test | Parking Lamps | The BCM activates the park lamp relay when you select ON. The park lamps illuminate until commanded OFF. |
| Light Test | Backup Lamps | The BCM activates the backup lamp output when you select ON. The backup lamps illuminate until commanded OFF. |
| Lamp Dimming Test | Dimming | The BCM adjusts the dimming output level when you select the percentage of illumination desired. The dimmable IP lamps will illuminate to the level set by the scan tool when the IP dimmer switch is in the FULL DIM position. |
Driver Door Module (DDM) Scan Tool Output Controls
| Scan Tool Output Control | Additional Menu Selection(s) | Description |
|---|---|---|
| Door Backlight Test | - | The DDM activates the driver door backlighting outputs when you select ON. The door backlighting will remain illuminated until commanded OFF. |
Passenger Door Module (PDM) Scan Tool Output Controls
| Scan Tool Output Control | Additional Menu Selection(s) | Description |
|---|---|---|
| Door Backlight Test | - | The DDM activates the passenger door backlighting outputs when you select ON. The door backlighting will remain illuminated until commanded OFF. |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.