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.
Circuit/System Description
Voltage is applied at all times to the low beam headlamp relay from battery voltage. Two different inputs to the body control module (BCM) can turn ON the low beam headlamps. The headlamp switch and the ambient light sensor.
Automatic Headlamps Operation
When the ambient light sensor detects a low light condition, the BCM then applies a ground to the headlamp low beam relay control circuit. This engages the headlamp relay and applies voltage through the headlamp fuses to the low beam headlamps.
Headlamp Switch Operation
When the headlamp switch is placed in the ON position, ground is applied to the BCM through the headlamp switch circuit. The BCM then applies a ground to the headlamp low beam relay control circuit. This engages the headlamp relay and applies voltage through the headlamp fuses to the low beam headlamps.
NO RELATED
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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.