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.
Theory Of Operation
The Smart Lighting Module - Left (SLML) and Smart Lighting Module - Right (SLMR) each receive voltage from the Power Distribution Center (PDC) Assembly, through a shared Fused B(+) circuit. A dedicated ground path is provided to the SLML and the SLMR through the wiring harness, attached to the body sheet metal. The Fused Ignition voltage signal from the PDC Assembly is only used by the Smart Lighting Modules (SLMs) to detect when the ignition is On and as a wake-up signal. The SLMs are mounted to the backside of the Front Lamp Assemblies and are serviced separately.
The Front Exterior Lighting system includes the following:
- Headlamp/Fog Lamp Switch
- Multifunction Switch
- Hazard Switch
- Body Control Module (BCM)
- SLML and SLMR
- Front Lamp Assemblies
- Front Sidemarker Lamps
The Body Control Module (BCM) receives all Front Exterior Lighting System activation requests. When the BCM receives an activation request for a Front Exterior Lamp, the BCM sends a CAN-FD Bus message to the SLMs, which activates the requested lamps.
The Smart Lighting Modules (SLMs) control the activation of the following:
- Park/Sidemarker Lamps
- Turn/Hazard Lamps
- Daytime Running Lamps (DRLs)
- Front Fog Lamps
- Low/High Beam Headlamps
The hard-wired Turn Lamp circuit between the BCM and SLMs is used as a redundant signal. When the Turn Lamps are activated, the BCM compares the signal on that circuit to the CAN Bus messages received from the SLMs. A DTC will set if the BCM detects the signal and message do not match.
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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.