The B1591 diagnostic trouble code (DTC) indicates a fault within the automatic headlamp delay decrease circuit. This circuit controls how long the headlights remain illuminated after the ignition is switched off, providing illumination for the driver to safely exit the vehicle and reach their destination. A failure in this circuit can result in the headlights turning off prematurely or not turning off at all, creating inconvenience and potential safety hazards.
This article provides a comprehensive overview of the B1591 code, including its symptoms, causes, diagnostic procedures, and potential solutions. Understanding this code and its associated issues is crucial for effective troubleshooting and repair.
B1591: Auto Lamp Delay Decrease Circuit Failure - Comprehensive Overview
| Topic | Description | Possible Causes |
|---|---|---|
| Symptoms | Headlights turning off sooner than expected after ignition is turned off. Headlights not turning off at all after the ignition is turned off. The auto headlamp delay function not working at all. Battery drain due to headlights remaining on. Erratic or unpredictable headlight behavior. | Faulty auto lamp control module. Wiring harness issues (damaged, shorted, open circuits). Corrosion or loose connections in the circuit. Faulty light sensor. Software glitches in the vehicle's computer system. Failed relay controlling the auto lamp delay function. Incorrect programming of the auto lamp control module. |
| Possible Causes | Faulty Auto Lamp Control Module: The module itself might be defective. Wiring Issues: Damaged wiring, short circuits, or open circuits in the auto lamp delay circuit. Corrosion/Loose Connections: Corrosion or loose connections can disrupt the electrical flow. Faulty Light Sensor: A malfunctioning light sensor can send incorrect signals. Software Glitches: Software issues in the vehicle's computer system. Failed Relay: A faulty relay controlling the delay function. Incorrect Programming: The auto lamp control module may be incorrectly programmed. | Aging of components. Exposure to harsh environmental conditions (moisture, heat). Physical damage to wiring or connectors. Electrical surges. Improper installation or repair. Manufacturing defects. Software updates gone wrong. |
| Diagnostic Steps | Check for related DTCs. Inspect wiring and connectors for damage or corrosion. Test the auto lamp control module. Test the light sensor. Verify proper voltage and ground to the auto lamp delay circuit. Use a scan tool to monitor the auto lamp delay function. Check the relay controlling the auto lamp delay. Check the vehicle's computer system for software updates. | Using a multimeter to check voltage and continuity. Using a scan tool to read DTCs and monitor sensor data. Visually inspecting wiring and connectors. Referring to the vehicle's service manual for wiring diagrams and testing procedures. Comparing sensor readings to known good values. Testing relays using a relay tester. |
| Common Solutions | Replace the faulty auto lamp control module. Repair or replace damaged wiring. Clean or replace corroded connectors. Replace the faulty light sensor. Reprogram the auto lamp control module. Replace the faulty relay. Update the vehicle's computer system software. | Properly diagnosing the root cause before replacing parts. Using high-quality replacement parts. Ensuring proper wiring and connections. Following the vehicle manufacturer's recommended repair procedures. Clearing DTCs after the repair is completed. Testing the system after the repair to ensure it is functioning correctly. |
| Tools Required | Scan tool. Multimeter. Wiring diagram. Connector cleaner. Terminal crimping tool. Wire stripper. Replacement parts (auto lamp control module, light sensor, relay, wiring connectors). Vehicle's service manual. Relay tester. | Access to vehicle-specific information. Proper safety equipment (gloves, eye protection). Adequate lighting. A clean and organized work area. Knowledge of automotive electrical systems. |
| Preventative Measures | Regularly inspect wiring and connectors for damage or corrosion. Protect wiring from harsh environmental conditions. Avoid overloading the electrical system. Address any electrical issues promptly. Keep the vehicle's computer system software up to date. | Parking the vehicle in a covered area. Avoiding driving through deep water. Properly maintaining the vehicle's battery. Using the correct type of fuses. Having the vehicle serviced regularly by a qualified technician. |
| Related DTCs | B1590 (Auto Lamp Control Module Malfunction). B1592 (Auto Lamp Sensor Circuit Malfunction). B1593 (Auto Lamp Relay Circuit Malfunction). B1594 (Auto Lamp Switch Circuit Malfunction). B1595 (Auto Lamp Power Supply Circuit Malfunction). | These codes can help narrow down the source of the problem. Addressing related codes first may resolve the B1591 issue. Understanding the relationship between these codes is important for accurate diagnosis. |
Detailed Explanations
Symptoms:
The symptoms of a B1591 code can vary depending on the severity of the fault. The most common symptom is the headlights turning off sooner than expected after the ignition is switched off. In some cases, the headlights may not turn off at all, leading to battery drain. The auto headlamp delay function may also stop working entirely. Erratic or unpredictable headlight behavior can also occur.
Possible Causes:
Several factors can contribute to a B1591 code. A faulty auto lamp control module is a common culprit, as this module is responsible for controlling the auto lamp delay function. Wiring issues, such as damaged wiring, short circuits, or open circuits in the auto lamp delay circuit, can also cause the code to appear. Corrosion or loose connections can disrupt the electrical flow and prevent the circuit from functioning correctly. A faulty light sensor can send incorrect signals to the control module, leading to improper headlight operation. Software glitches in the vehicle's computer system can also cause the code to appear. A failed relay controlling the delay function can also be the cause. Finally, incorrect programming of the auto lamp control module can also lead to this issue.
Diagnostic Steps:
A systematic approach is necessary to diagnose the root cause of a B1591 code. Begin by checking for any related DTCs, as these can provide valuable clues. Next, carefully inspect the wiring and connectors for any signs of damage or corrosion. The auto lamp control module and light sensor should be tested to ensure they are functioning correctly. Verify proper voltage and ground to the auto lamp delay circuit using a multimeter. A scan tool can be used to monitor the auto lamp delay function and identify any abnormalities. Check the relay controlling the auto lamp delay. Finally, check the vehicle's computer system for any available software updates.
Common Solutions:
The appropriate solution for a B1591 code depends on the underlying cause. Replacing the faulty auto lamp control module is often necessary. Damaged wiring should be repaired or replaced. Corroded connectors should be cleaned or replaced. A faulty light sensor should be replaced. In some cases, reprogramming the auto lamp control module may be necessary. A faulty relay should be replaced. Updating the vehicle's computer system software can also resolve the issue.
Tools Required:
Diagnosing and repairing a B1591 code requires a variety of tools. A scan tool is essential for reading DTCs and monitoring sensor data. A multimeter is needed to check voltage and continuity. A wiring diagram is crucial for understanding the circuit layout. Connector cleaner can be used to remove corrosion from connectors. A terminal crimping tool and wire stripper are necessary for repairing wiring. Replacement parts, such as the auto lamp control module, light sensor, relay, and wiring connectors, may be required. The vehicle's service manual provides valuable information on testing procedures and repair instructions. A relay tester can be used to test the functionality of relays.
Preventative Measures:
Several preventative measures can help avoid B1591 codes. Regularly inspect wiring and connectors for damage or corrosion. Protect wiring from harsh environmental conditions. Avoid overloading the electrical system. Address any electrical issues promptly. Keep the vehicle's computer system software up to date.
Related DTCs:
Several other DTCs are related to the auto lamp system. B1590 (Auto Lamp Control Module Malfunction) indicates a general malfunction of the control module. B1592 (Auto Lamp Sensor Circuit Malfunction) points to a problem with the light sensor circuit. B1593 (Auto Lamp Relay Circuit Malfunction) indicates a fault in the relay circuit. B1594 (Auto Lamp Switch Circuit Malfunction) suggests an issue with the auto lamp switch. B1595 (Auto Lamp Power Supply Circuit Malfunction) indicates a problem with the power supply to the auto lamp system.
Frequently Asked Questions
What does the B1591 code mean?
The B1591 code indicates a fault in the auto lamp delay decrease circuit, which controls how long the headlights stay on after the ignition is turned off. This circuit is crucial for providing sufficient light when exiting the vehicle.
What are the symptoms of a B1591 code?
Common symptoms include headlights turning off too quickly, not turning off at all, or the auto headlamp delay function not working. These symptoms can lead to inconvenience and potential safety issues.
What causes the B1591 code?
Possible causes include a faulty auto lamp control module, wiring issues, corrosion, a faulty light sensor, software glitches, or a failed relay. Identifying the specific cause is crucial for effective repair.
How do I diagnose a B1591 code?
Diagnosis involves checking for related DTCs, inspecting wiring and connectors, testing the auto lamp control module and light sensor, and verifying proper voltage and ground. A scan tool and multimeter are essential tools for this process.
How do I fix a B1591 code?
Fixing the B1591 code may involve replacing the faulty auto lamp control module, repairing damaged wiring, cleaning corroded connectors, replacing the faulty light sensor, or reprogramming the control module. Proper diagnosis is essential before attempting any repairs.
Conclusion
The B1591 Auto Lamp Delay Decrease Circuit Failure code indicates a problem with the system that controls the headlight delay function. Accurate diagnosis and repair, following a systematic approach, are crucial for restoring proper headlight operation and ensuring driver safety. Always refer to the vehicle's service manual for specific instructions and safety precautions.