OBD-II DTC B1791 – Autolamp Sensor Input Circuit Open
DTC B1791 meaning
DTC B1791 refers to an issue with the autolamp sensor input circuit, indicating that there is an open circuit condition. This means that the vehicle’s onboard diagnostic system has detected that the signal from the autolamp sensor is not being received properly, which can affect the automatic headlight operation.
DTC B1791 symptoms
Common symptoms associated with DTC B1791 may include:
- Headlights not turning on automatically
- Dashboard warning lights illuminated
- Manual control of headlights required
- Inconsistent headlight operation
DTC B1791 causes
The causes of DTC B1791 can include:
- Faulty autolamp sensor
- Open or shorted wiring in the sensor circuit
- Corroded or damaged connectors
- Faulty body control module (BCM)
DTC B1791 seriousness
DTC B1791 is considered a moderate issue. While it may not prevent the vehicle from operating, it can lead to safety concerns due to improper headlight functionality. It is advisable to address this issue promptly to ensure proper visibility during nighttime driving or adverse weather conditions.
How to diagnose DTC B1791
To diagnose DTC B1791, follow these steps:
- Use an OBD-II scanner to confirm the presence of DTC B1791.
- Inspect the autolamp sensor and its wiring for visible damage or disconnections.
- Check the continuity of the sensor circuit using a multimeter.
- Test the autolamp sensor for proper operation.
- Examine the body control module for any faults or issues.
How to fix DTC B1791 step-by-step instructions
To fix DTC B1791, follow these steps:
- Inspect and repair any damaged wiring or connectors in the autolamp sensor circuit.
- Replace the autolamp sensor if it is found to be faulty.
- Ensure all connections are secure and free from corrosion.
- Test the system to confirm that the headlights operate correctly.
- Clear the DTC using an OBD-II scanner and perform a road test to verify the fix.
How to erase DTC B1791
To erase DTC B1791, follow these steps:
- Connect an OBD-II scanner to the vehicle’s diagnostic port.
- Access the diagnostic menu and select the option to clear or erase trouble codes.
- Confirm the action and wait for the scanner to complete the process.
- Disconnect the scanner and start the vehicle to check if the code reappears.
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