What Does B1587 Mean?
B1587 indicates the Body Control Module (BCM) has detected a fault in the autolamp delay increase circuit, which controls the time headlights remain on after the vehicle is turned off. The BCM monitors this circuit and sets this code when it detects an open circuit, short to ground, short to power, or excessive resistance in the delay increase switch or wiring. This affects the automatic headlight delay feature that provides illumination after exiting the vehicle.
Common Causes
45%
Faulty autolamp delay switch or rocker switch assembly with internal contact failure
30%
Damaged wiring or corroded connector between autolamp delay switch and BCM
15%
Failed Body Control Module with internal circuit damage
10%
Short circuit to power or ground in delay circuit wiring
Diagnostic Steps
1
Step 1: Perform visual inspection of autolamp delay switch assembly and headlight switch for physical damage, burnt contacts, or signs of water intrusion. Check switch operation manually for binding or erratic behavior.
2
Step 2: Using a digital multimeter, backprobe the autolamp delay switch connector and verify supply voltage (typically 5V or 12V reference) and ground circuit integrity. Check for continuity through the switch in both positions and verify resistance values match factory specifications (typically 0-10k ohms range).
3
Step 3: Inspect wiring harness from switch to BCM for chafing, pinching, or damage. Pay special attention to areas where harness passes through firewalls or flex points. Check all connectors for bent pins, corrosion, or pushed-out terminals.
4
Step 4: With switch disconnected, measure resistance of delay circuit at BCM connector. Resistance should be infinite (open circuit) with switch disconnected. Check for shorts to power (should read battery voltage if shorted) or shorts to ground (should read 0 ohms if shorted).
5
Step 5: If all wiring and switch test normally, test BCM signal input circuit by applying appropriate resistance values at BCM connector using a decade box to simulate switch positions while monitoring BCM response with scan tool. BCM should recognize different delay settings.
6
Step 6: Replace faulty component (switch or BCM based on test results), clear codes, and verify autolamp delay function operates correctly through multiple cycles. Confirm code does not return after test drive.
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
B1587 indicates the Body Control Module (BCM) has detected a fault in the autolamp delay increase circuit, which controls the time headlights remain on after the vehicle is turned off. The BCM monitors this circuit and sets this code when it detects an open circuit, short to ground, short to power, ...
The most common cause of B1587 (Autolamp Delay Increase Circuit Failure) is: Faulty autolamp delay switch or rocker switch assembly with internal contact failure
Typical repair costs for B1587 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this only affects the convenience feature that delays headlights after ignition off. Normal headlight operation is not affected, though you may lose automatic delay functionality and need to manually turn off headlights.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1587 to identify the root cause.
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Quick Info
Category
Body
System
Body Control and Lighting System
Difficulty
Type
Manufacturer
Recommended Tools
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