B1591 – Autolamp Delay Decrease Circuit Failure
The ODBII code B1591 indicates a malfunction in the autolamp delay decrease circuit, which is responsible for controlling the duration that the vehicle’s lights remain on after the ignition is turned off.
The severity of ODBII code B1591 is generally considered moderate.
Common Causes For: B1590 Autolamp Delay Increase Circuit Short To Ground
- Faulty autolamp control module
- Damaged wiring or connectors
- Short circuit in the autolamp delay circuit
- Open circuit in the autolamp delay circuit
- Malfunctioning headlight switch
- Corroded or loose electrical connections
- Failed relay associated with the autolamp system
- Software issues in the vehicle’s control module
Common misdiagnosis for B1591 Autolamp Delay Decrease Circuit Failure
- Faulty Body Control Module (BCM)
- Defective headlight switch
- Wiring issues or shorts in the circuit
- Malfunctioning autolamp sensor
- Incorrectly programmed BCM
- Faulty relay or fuse related to lighting
- Issues with the vehicle’s lighting control system
Common Troubleshooting Steps
The OBD-II code B1591 refers to a fault in the Autolamp Delay Decrease Circuit, which is part of the vehicle’s lighting control system. When troubleshooting this code, you can follow these common steps:
- Check for Additional Codes: Use an OBD-II scanner to check for any other related trouble codes. This can provide more context and help identify if there are multiple issues.
- Inspect the Wiring and Connectors: Visually inspect the wiring and connectors associated with the autolamp system. Look for signs of damage, corrosion, or loose connections that could affect the circuit.
- Test the Autolamp Switch: The autolamp switch may be faulty. Test the switch for proper operation and continuity. If the switch is not functioning correctly, it may need to be replaced.
- Check the Fuses: Inspect the fuses related to the lighting system. A blown fuse can interrupt the circuit and cause the code to trigger.
- Examine the Control Module: The Body Control Module (BCM) or Lighting Control Module (LCM) may be malfunctioning. Check for any software updates or known issues with the module. If necessary, perform a reset or reprogram the module.
- Test the Autolamp Delay Circuit: Use a multimeter to test the voltage and ground at the autolamp delay circuit. Ensure that the circuit is receiving the correct voltage and that there are no shorts or open circuits.
- Inspect Related Components: Check other components that may be related to the autolamp system, such as relays or sensors. Ensure they are functioning properly.
- Perform a System Reset: After addressing any issues found, clear the trouble codes and perform a system reset. Then, take the vehicle for a test drive to see if the code returns.
- Consult Repair Manuals or Technical Service Bulletins (TSBs): Look for any specific repair procedures or TSBs related to the B1591 code for your vehicle make and model.
- Seek Professional Help: If the issue persists after performing these steps, it may be best to consult a professional mechanic or technician who has experience with your vehicle’s electrical systems. By following these steps, you should be able to diagnose and potentially resolve the issue related to the B1591 code.