Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
The cost of diagnosing the B1791 code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle's make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
The Smart Junction Box (SJB) sends a voltage signal to the headlamp switch and the light sensor.
When the headlamp switch is placed in the AUTOLAMPS ON position, the voltage signal is routed to ground. When the SJB detects the headlamp switch in the AUTOLAMPS ON position, the SJB monitors the light sensor input. The light sensor determines the amount of light based on the input received from the ambient lighting conditions. When the ambient level has reached a point (determined by the internal programming of the SJB ), the SJB provides voltage to the headlamps, parking and license plate lamps. The Diagnostic Trouble Code (DTC) sets when the SJB detects an open from the light sensor input circuit.
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