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AutoCodes - Generic - B1791

B1791 Code - Autolamp Sensor Input Circuit Open

- Code Popularity: 7,637 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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By - Updated Oct 16, 2022
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|Code B1791 Possible Causes

  • Faulty Light Sensor
  • Light Sensor harness is open or shorted
  • Light Sensor circuit poor electrical connection
  • Faulty Headlamp Switch
  • Faulty Smart Junction Box (SJB)

|How do I Fix the Code B1791?

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.

Does your Car have Safety Recalls? → Check here

|What is the Cost to Diagnose the Code B1791?

Labor: 1.0

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.

|What are Code B1791 Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

|Code B1791 Description

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.

OBDII Code B1791 - Autolamp Sensor Input Circuit Open -
B1791 Code - Autolamp Sensor Input Circuit Open

|Need More Information on the B1791 Code?

Need more information on how to fix the B1791 code? Get Access to Factory Service Manuals

|Information for Specific Makes

|Need Help with the B1791 Code?

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|Code B1791 comments

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