B1587 — Autolamp Delay Increase Circuit Failure

The diagnostic trouble code B1587 indicates a problem within the autolamp delay circuit, specifically related to an increase or malfunction in the delay time before headlamps turn off. Essentially, it suggests that the automatic lighting system is not operating within its designated parameters, often causing the vehicle’s lights to stay on longer than intended or delay turning off after switching off the ignition.

Note: Label variations or code descriptions may differ slightly between different vehicle manufacturers, but the core issue remains related to the autolamp delay system.

Fast Facts

System affected: Autolamp/Lighting System
Severity: Moderate — may impact visibility and battery drain if unresolved
Main symptoms: Headlamps staying on longer than usual, warning lights, or error messages on the dashboard
Driveability: Yes — but with potential electrical or lighting concerns

Manufacturer variations for trouble code B1587

Different vehicle manufacturers may use varying labels or specific coding identifiers for similar issues. Recognising these can help in precise diagnostics. Here are some known variations:

Volkswagen / Audi: Possible label variations such as « 93-00 – Autolight Circuit » or « Child Lock Relay Fault »
Ford: Similar issues may be logged under codes related to the lighting delay system, sometimes as « Lighting Delay Circuit Malfunction »
BMW / Mini: Variations such as « Auto Light Delay Circuit Error »
Mercedes-Benz: May appear as « Lighting Control Module Fault » with subcodes correlating to the delay circuit

What does trouble code B1587 mean?

In simple terms, B1587 is a diagnostic code that indicates an abnormality within the vehicle’s autolamp delay circuit. The Engine Control Unit (ECU) — which is the vehicle’s brain managing various electronic systems — monitors the timing and operation of the auto lighting feature. This code usually appears when the delay before headlamps turn off after you switch off the ignition becomes longer than the manufacturer’s specified duration.

The cause typically involves a malfunction or degradation in the circuit controlling the delay mechanism, which may involve sensors, relays, or control modules. Sometimes, environmental factors or electrical interference may trigger the code, especially if the circuit components are exposed to moisture, dirt, or damage.

What triggers the code: The ECU detects that the autolamp delay duration exceeds the programmed or expected value, or a feedback loop signals an abnormal condition in the lighting delay circuit.

Typical context of appearance: The code may appear after replacing the lighting switch, repairing wiring, or after electrical system disturbances. It may also manifest during routine lighting system checks or when warning lights on the dash occur unexpectedly.

Severity and risks of trouble code B1587

The B1587 code is generally classified as a moderate issue. If left unresolved, the main risks include increased battery drain due to lights remaining on longer than necessary and potential electrical wear on the lighting components. Importantly, this fault does not typically affect vehicle safety or drivability directly, but it might cause driver inconvenience or lead to electrical system issues if not addressed.

**Can the vehicle be driven?** The answer is Yes in most cases, but caution is advised. Persistent lighting anomalies could potentially drain the battery or cause other electrical malfunctions. It’s recommended to diagnose and fix the issue promptly to prevent further complications.

Symptoms of trouble code B1587

When this code is active, you might notice specific signs that point towards a malfunction in the autolamp delay circuit. These symptoms include:

Headlamps stay on longer: The most common symptom is the headlamps not turning off immediately after switching off the ignition, resulting in prolonged illumination.
Warning messages: Some vehicles display alerts or warning lights related to lighting system faults on the dashboard.
Intermittent lighting issues: Flickering or inconsistent headlamp operation may be observed.
Unusual delay before lights turn off: Noticeable delay in headlamp shutdown compared to normal operation.

Most likely causes of trouble code B1587

Understanding the root causes can significantly streamline diagnostics and repairs. The following causes are listed from most common to less frequent:

Faulty autolamp delay relay or control module: The relay or central control unit responsible for controlling the delay may malfunction due to internal failure or electrical issues.
Damaged or corroded wiring and connectors: Exposure to moisture, dirt, or physical damage may cause poor electrical contact or short circuits.
Dirty or malfunctioning light sensors: Sensors that detect ambient light levels vital for automatic operation might be defective or dirty, affecting the delay timing.
Aftermarket modifications or improper repairs: Non-OEM additions or previous repairs may have introduced electrical instability or wiring conflicts affecting the delay circuit.
Software/firmware glitches: Occasionally, a software error may erroneously trigger this code, particularly after updates or reprogramming.

How to diagnose trouble code B1587

Diagnosis involves a systematic approach to verify electrical integrity and proper operation of the autolamp delay system:

Visual inspection: Check wiring harnesses, connectors, and relays related to the lighting system for corrosion, damage, or loose connections.
Clean sensors and connectors: Ensure ambient light sensors and associated connectors are free of dirt and corrosion.
Perform live data monitoring: Using a compatible scan tool, observe the autolamp delay status, relay activation, and sensor inputs during vehicle operation.
Test relay operation: Confirm that relays controlling the delay circuit are functioning correctly with a multimeter or relay tester.
Check for software updates or reinitialisation: Verify if firmware updates are available for the body control module or lighting control units, and perform reprogramming if necessary.

Possible repairs for trouble code B1587

Once the root cause has been identified, repairs can be directed accordingly. The necessary actions may involve:

Replacing faulty relays or control modules: A professional repair shop or qualified technician should perform these replacements to ensure proper operation.
Repair or replace damaged wiring and connectors: Conductive connections must be restored or replaced, often considered a basic repair but requiring technical skill.
Cleaning or replacing sensors: Ambient light sensors or associated components should be cleaned or swapped if faulty. This is a straightforward repair.
Reprogramming or updating software: ECU firmware updates may resolve glitches; this process typically requires specialised diagnostic equipment and should be performed by professionals.
Reinstallation of proper OEM parts: Using genuine parts ensures compatibility and long-term reliability.

Vehicles commonly associated with trouble code B1587 in Europe

The B1587 fault code can be found across multiple makes and models, particularly those equipped with automatic lighting systems. While the exact prevalence varies, vehicles from the following brands are known to sometimes exhibit this fault:

Volkswagen Group: Volkswagen, Audi, Škoda, SEAT — especially models from the last decade with advanced lighting features
Ford: Focus, Fiesta, Mondeo — especially models with automatic lighting functions
BMW / Mini: Various series with integrated ambient light sensors and auto lighting systems
Mercedes-Benz: Commonly in models with adaptive lighting or intelligent light control modules

Frequent mistakes with trouble code B1587

Diagnosing and repairing this issue can sometimes be complicated by common errors, which may prolong troubleshooting or lead to ineffective repairs. These mistakes include:

Misidentifying the root cause: Replacing parts without verifying the circuits or sensor activity can lead to unnecessary expenses.
Ignoring wiring or connector issues: Electrical faults often involve simple fixes such as cleaning contacts or repairing damaged wiring, which are overlooked.
Overlooking environmental factors: External conditions like moisture or dirt can impact sensors or relays without being immediately apparent.
Performing software resets without proper reinitialisation: Clearing codes without addressing underlying hardware problems can cause the fault to reappear.
Working without proper diagnostic tools: Attempting repairs without suitable scan tools or electrical testers can lead to incomplete diagnostics.

FAQ — trouble code B1587

Can this code disappear on its own?
In most cases, B1587 does not resolve itself naturally. The fault persists until diagnosed and repaired, especially if related to hardware malfunction.

Can I keep driving?
Yes, the vehicle can generally be driven, but it’s advisable to have the issue diagnosed soon. Prolonged faulty lighting behavior may drain the battery or cause additional electrical problems.

Why does the code return after clearing it?
If the underlying hardware issue, such as a faulty relay or corroded wiring, is not addressed, the code will likely return after clearing. Ensuring all hardware and wiring are in good condition is essential for a lasting fix.