B1791 Lincoln Code - Autolamp Sensor Input Circuit Open
Quick Answer
The Smart Junction Box (SJB) sends a voltage signal to the headlamp switch and the light sensor. Common causes include Faulty Light Sensor, Light Sensor harness is open or shorted, Light Sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- B1791 Lincoln indicates Autolamp Sensor Input Circuit Open.
- Common causes
- Common causes include Faulty Light Sensor, Light Sensor harness is open or shorted, Light Sensor circuit poor electrical connection.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code B1791 Lincoln Description
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.
What are the Possible Causes of the DTC B1791 Lincoln?
- 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 to Fix the DTC B1791 Lincoln?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the B1791 Lincoln code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
Need more information about the B1791 Lincoln code?
Need more information on how to fix the B1791 Lincoln code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the B1791 Lincoln code diagnosed by a professional: Find a repair shop in your area
Frequently Asked Questions about B1791 Lincoln Code
1. What are the common symptoms of OBDII code B1791 Lincoln (Autolamp Sensor Input Circuit Open)?
- Common symptoms include the automatic headlights not working, the autolamp sensor not responding, or the dashboard warning light being illuminated.
2. What typically causes the Autolamp Sensor Input Circuit Open code (B1791) in a Lincoln vehicle?
- The code is usually triggered by a fault in the autolamp sensor circuit, which can be caused by damaged wiring, a malfunctioning sensor, or a faulty control module.
3. How can I diagnose the Autolamp Sensor Input Circuit Open issue in my Lincoln vehicle?
- Diagnosis involves inspecting the autolamp sensor wiring for damage, testing the sensor's functionality, and checking the control module for proper operation using a diagnostic scanner.
4. Can I drive my Lincoln with the Autolamp Sensor Input Circuit Open code (B1791) triggered?
- While it may be safe to drive, it is recommended to address the issue promptly to ensure the automatic lighting system functions correctly for your safety and compliance with regulations.
5. How can I repair the Autolamp Sensor Input Circuit Open code (B1791) in my Lincoln?
- Repair may involve repairing or replacing damaged wiring, replacing a faulty autolamp sensor, or reprogramming the control module to resolve the circuit open issue.
6. Are there any DIY tips for fixing the Autolamp Sensor Input Circuit Open code in a Lincoln vehicle?
- DIY enthusiasts may attempt to visually inspect the wiring, clean the sensor connections, or check for loose connections before seeking professional assistance.
7. How much does it typically cost to fix the Autolamp Sensor Input Circuit Open code in a Lincoln vehicle?
- The cost of repair can vary depending on the root cause of the issue, but it may range from $100 to $500, including parts and labor.
8. Will resetting the OBDII code B1791 in my Lincoln vehicle make the issue go away permanently?
- Resetting the code may temporarily turn off the warning light, but the underlying issue causing the code will persist until it is properly diagnosed and repaired.
9. What should I do if I continue to experience the Autolamp Sensor Input Circuit Open code after repair?
- If the code reappears after repair, it is advisable to recheck the wiring, sensor, and control module for any overlooked issues or seek assistance from a professional mechanic.
10. Is it important to fix the Autolamp Sensor Input Circuit Open code in my Lincoln vehicle even if the automatic lighting is not a priority for me?
- Yes, resolving the code is crucial not only for the proper functioning of the autolamp sensor system but also for maintaining the overall health and performance of your vehicle's electrical system.
Discuss the causes and fixes for B1791 Lincoln OBDII Code
Code B1791 Lincoln comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
