Autolamp Delay Increase Circuit Failure
The vehicle's automatic headlight delay system isn't working properly, similar to a dimmer switch that's stuck and won't respond to commands. The body control module detected a malfunction in the circuit that controls how long lights stay on after the engine shuts off.
The body control module monitors voltage and resistance in the autolamp delay circuit to verify proper relay operation and timing control. It measures the circuit's ability to energize and de-energize the headlight relay at programmed intervals after ignition off. If voltage drops, resistance spikes, or timing deviates beyond acceptable thresholds, a fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Relay Coil Voltage | 11-14.5V during activation | <9V or >15V sustained |
| Delay Timer Response | 30-180 second hold time | No response or fails to release within 10 seconds |
Code B1587 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.
Once the fault is repaired, B1587 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.