B1591 – OBD-II DTC

OBD-II DTC B1591 – Autolamp Delay Decrease Circuit Failure

DTC B1591 meaning

DTC B1591 refers to a fault in the Autolamp Delay Decrease Circuit. This diagnostic trouble code indicates that the vehicle’s system has detected a malfunction in the circuit responsible for controlling the delay feature of the autolamps, which are designed to automatically turn on and off based on ambient light conditions.

DTC B1591 symptoms

Common symptoms associated with DTC B1591 may include:

• Autolamps not functioning as intended
• Inconsistent operation of the headlight delay feature
• Dashboard warning lights illuminated
• Increased battery drain due to lights staying on longer than necessary

DTC B1591 causes

Several factors can lead to the occurrence of DTC B1591, including:

• Faulty wiring or connectors in the autolamp circuit
• Defective autolamp control module
• Malfunctioning sensors that detect ambient light
• Software issues within the vehicle’s control modules

DTC B1591 seriousness

The seriousness of DTC B1591 can vary. While it may not pose an immediate safety risk, it can lead to:

• Increased risk of battery drain
• Inconvenience due to improper lighting operation
• Potential for further electrical issues if left unaddressed

How to diagnose DTC B1591

To diagnose DTC B1591, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the code.
2. Inspect the wiring and connectors related to the autolamp circuit for damage or corrosion.
3. Check the autolamp control module for proper operation.
4. Test the ambient light sensors to ensure they are functioning correctly.
5. Review any related codes that may provide additional context.

How to fix DTC B1591 step-by-step instructions

To fix DTC B1591, follow these steps:

1. Repair or replace any damaged wiring or connectors found during diagnosis.
2. Replace the autolamp control module if it is determined to be faulty.
3. Ensure that ambient light sensors are clean and functioning replace if necessary.
4. Update the vehicle’s software if applicable, following manufacturer guidelines.
5. Clear the DTC using an OBD-II scanner and test the system to ensure proper operation.

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