B2587 - Park Lamp Relay Output Circuit Low (BCM)

Introduction:

The B2587 diagnostic trouble code (DTC) indicates a problem within the park lamp relay output circuit, specifically a low voltage condition detected by the Body Control Module (BCM). This code suggests that the BCM is not seeing the expected voltage level on the circuit it uses to control the park lamp relay, potentially leading to non-functional parking lights. Addressing this issue promptly is crucial for vehicle safety and compliance with road regulations.

Comprehensive Breakdown of B2587

Detailed Explanations

Code Definition: B2587 - Park Lamp Relay Output Circuit Low (BCM)

This code signifies that the Body Control Module (BCM), the central computer responsible for managing various electrical functions in your vehicle, has detected a lower than expected voltage on the circuit it uses to control the park lamp relay. The BCM sends a signal to the relay to activate the parking lights. When the BCM detects a low voltage instead of the expected voltage, it sets the B2587 code. This discrepancy suggests a problem either with the BCM's output, the wiring between the BCM and the relay, or the relay itself.

Symptoms

The most obvious symptom is non-functional parking lights. However, other symptoms may include intermittent operation of the parking lights, or in some cases, other lighting malfunctions if the park lamp circuit shares components with other lighting systems. It is also possible for the BCM to store the code without any immediately noticeable symptoms. In rare scenarios, if the relay is stuck in an "on" position due to the fault, it could lead to a increased drain on the vehicle's battery, although this is less likely with a "low" code as it usually indicates a lack of sufficient power.

Possible Causes

• Faulty Park Lamp Relay: The relay is an electromechanical switch that controls the flow of power to the park lamps. It can fail due to wear and tear, corrosion, or electrical damage.
• Wiring Issues: Damaged, corroded, or shorted wiring can disrupt the flow of electricity in the park lamp circuit. This includes the wiring between the BCM and the relay, and the wiring from the relay to the park lamps.
• BCM Malfunction: While less common, the BCM itself could be faulty, providing an incorrect or low voltage signal to the relay.
• Grounding Issues: A poor or missing ground connection can cause voltage drops and trigger the code. Ensure the ground connections for the park lamps and the BCM are clean and secure.
• Fuse Issues: A blown or damaged fuse in the park lamp circuit can interrupt voltage supply.
• Connector Problems: Loose, corroded, or damaged connectors at the BCM, relay, or park lamps can create resistance and voltage drops.
• Aftermarket Accessories: Improperly installed aftermarket lighting or other electrical accessories can interfere with the park lamp circuit and cause the code to set.

Diagnostic Steps

1. Visual Inspection: Begin by visually inspecting all wiring, connectors, and fuses related to the park lamp circuit for any signs of damage, corrosion, or looseness. Pay close attention to the wiring harness near the relay and the BCM.
2. Relay Testing: Test the park lamp relay itself using a multimeter to verify proper operation. You can also try swapping it with a known good relay to see if the problem is resolved.
3. Voltage Testing: Use a multimeter to measure the voltage at the park lamp relay control circuit, both at the BCM output and at the relay connector. Compare the readings to the manufacturer's specifications. A low voltage reading at the BCM output suggests a BCM problem, while a low voltage reading at the relay connector suggests a wiring issue.
4. Ground Circuit Testing: Verify the integrity of the ground circuit for the park lamps and the BCM. Use a multimeter to check for continuity between the ground point and the vehicle's chassis.
5. BCM Input/Output Testing: If other components test okay, the BCM input and output signal should be tested. This often requires specialized tools and knowledge and may be best left to a qualified technician.
6. Wiring Continuity Testing: Use a multimeter to check the continuity of the wiring between the BCM, the relay, and the park lamps. This will help identify any breaks or shorts in the wiring.
7. Fuse Check: Inspect all fuses related to the park lamp circuit for blown fuses. Replace any blown fuses with the correct amperage rating.
8. Scan Tool Data: Use a scan tool to monitor the BCM's output signal to the park lamp relay and any related data parameters. This can provide valuable information about the BCM's operation.
9. Consult Wiring Diagrams: Refer to the vehicle's wiring diagrams for the park lamp circuit to understand the circuit layout and identify potential problem areas. These diagrams are typically found in the vehicle's service manual.

Potential Repair Costs

The cost of repairing a B2587 code can vary depending on the cause of the problem.

• Fuse Replacement: Relatively inexpensive, typically costing between $5 and $15.
• Relay Replacement: A new relay can cost between $15 and $50.
• Wiring Repair: The cost of wiring repair can vary greatly depending on the severity and location of the damage. Expect to pay between $50 and $200 or more.
• BCM Replacement/Reprogramming: This is the most expensive repair option, with costs ranging from $200 to $1000 or more. BCM replacement often requires programming to match the vehicle's specific configuration.
• Labor Costs: Labor costs can vary depending on the shop and location, but expect to pay between $75 and $150 or more per hour.

Severity

The severity of the B2587 code is moderate to high. While the parking lights themselves may seem minor, their malfunction can lead to reduced visibility, increased risk of accidents, and potential legal issues. It's best to address the issue as soon as possible.

Related Codes

Several other DTCs may be related to the B2587 code. These include:

• B2586 - Park Lamp Relay Output Circuit High (BCM)
• Various other lighting circuit codes
• BCM communication codes

Technical Considerations

• Circuit Load: The park lamp circuit often powers multiple bulbs, so the total load on the circuit can be significant. This can contribute to voltage drops, especially if there are corroded connections or damaged wiring.
• Voltage Drop Testing: Performing voltage drop tests across the circuit is crucial for identifying areas of high resistance. This involves measuring the voltage drop across different sections of the circuit while the lights are turned on.
• BCM Programming: In some cases, replacing the BCM may require programming or calibration to match the vehicle's configuration. This is typically done by a qualified technician using specialized tools.

Frequently Asked Questions

• What does the B2587 code mean? The B2587 code indicates a low voltage condition in the park lamp relay output circuit, detected by the Body Control Module (BCM). This suggests a problem with the BCM's signal to the relay, the wiring, or the relay itself.

• Can I drive with a B2587 code? While you can drive, it's not recommended. The lack of functioning parking lights can reduce visibility and increase the risk of accidents, potentially violating traffic laws.

• Is the B2587 code serious? Yes, the B2587 code is considered moderately serious. It indicates a problem with the parking lights, which are essential for safety.

• How do I fix a B2587 code? Fixing the code involves diagnosing and repairing the underlying cause, which could be a faulty relay, wiring issues, a bad BCM, or a grounding problem. A systematic approach involving visual inspection, component testing, and voltage measurements is necessary.

• Can a bad fuse cause the B2587 code? Yes, a blown or damaged fuse in the park lamp circuit can interrupt voltage supply and trigger the B2587 code. Always check the fuses first.

Conclusion

The B2587 code signifies a problem with the park lamp relay output circuit, specifically a low voltage condition detected by the BCM. A systematic diagnostic approach, starting with a visual inspection and component testing, is crucial for identifying and resolving the issue, ensuring the proper functioning of the vehicle's parking lights and overall safety. Remember to consult wiring diagrams and seek professional assistance if needed.