The B2602 diagnostic trouble code (DTC) indicates a problem within the Daytime Running Lamp (DRL) circuit, specifically a low voltage condition as detected by the Body Control Module (BCM). This code suggests that the BCM is not receiving the expected voltage from the DRL circuit, which can lead to the DRLs not functioning properly. Addressing this issue promptly is crucial for maintaining vehicle safety and ensuring compliance with local traffic regulations.
| Category | Description | Possible Causes |
|---|---|---|
| Definition | B2602 Daytime Running Lamp (DRL) Circuit Low (BCM) | The BCM has detected a voltage in the DRL circuit that is below the expected threshold. |
| Symptoms | DRLs not illuminating | One or both DRLs failing to turn on when the vehicle is running. |
| Intermittent DRL operation | DRLs flickering or turning on and off sporadically. | |
| DRLs operating dimly | DRLs are on, but significantly dimmer than usual. | |
| Warning light illumination | A dashboard warning light (e.g., check engine light, DRL indicator) may be illuminated. | |
| Possible Causes | Faulty DRL bulb(s) | Burned-out or damaged DRL bulbs. |
| Wiring issues | Damaged, corroded, or loose wiring connections in the DRL circuit. | |
| Faulty DRL relay | A malfunctioning relay responsible for controlling the DRLs. | |
| Faulty DRL module (if equipped) | A defective DRL control module. | |
| Corroded or loose ground connection | A poor ground connection in the DRL circuit. | |
| Faulty Body Control Module (BCM) | Although less common, a malfunctioning BCM can cause this code. | |
| Blown fuse | A blown fuse in the DRL circuit. | |
| Diagnostic Steps | Visual inspection | Check DRL bulbs, wiring, and connectors for damage or corrosion. |
| Fuse check | Inspect the DRL fuse and replace if blown. | |
| Bulb test | Test the DRL bulbs using a multimeter or by swapping with known good bulbs. | |
| Wiring continuity test | Use a multimeter to check the continuity of the wiring in the DRL circuit. | |
| Voltage drop test | Perform a voltage drop test to identify areas of excessive resistance in the circuit. | |
| Relay test | Test the DRL relay to ensure it is functioning correctly. | |
| Ground connection check | Inspect and clean the ground connection for the DRL circuit. | |
| BCM diagnosis | If all other components check out, the BCM may need to be diagnosed by a qualified technician. | |
| Common Solutions | Replace faulty DRL bulb(s) | Replacing burned-out or damaged DRL bulbs. |
| Repair wiring | Repairing or replacing damaged, corroded, or loose wiring. | |
| Replace faulty DRL relay | Replacing a malfunctioning DRL relay. | |
| Replace faulty DRL module | Replacing a defective DRL control module (if equipped). | |
| Clean ground connection | Cleaning and tightening the ground connection for the DRL circuit. | |
| Replace blown fuse | Replacing a blown fuse in the DRL circuit. | |
| BCM replacement/reprogramming | In rare cases, the BCM may need to be replaced or reprogrammed. | |
| Related Codes | B2600 - Daytime Running Lamp Control Circuit High | Indicates a high voltage condition in the DRL circuit. |
| B2601 - Daytime Running Lamp Control Circuit Range/Performance | Indicates that the DRL circuit is not performing as expected. | |
| B2603 - Daytime Running Lamp Control Circuit Open | Indicates an open circuit in the DRL circuit. | |
| Severity | Moderate | While not immediately disabling, a B2602 code can lead to safety concerns and potential legal issues due to non-functional DRLs. |
| Maintenance | Regular inspection of DRLs | Periodically check the DRLs to ensure they are functioning correctly. |
| Proper wiring maintenance | Keep wiring and connectors clean and free from corrosion. | |
| Tools Required | Multimeter | For testing voltage, continuity, and resistance. |
| Wiring diagrams | To understand the DRL circuit layout. | |
| Socket set/wrenches | For removing and installing components. | |
| Wire stripper/crimper | For repairing wiring. | |
| Test light | For quick voltage checks. | |
| Location of Components | DRL Bulbs | Typically located in the headlight assembly or a separate housing. |
| DRL Relay | Usually found in the under-hood fuse box or a relay panel. | |
| DRL Module | Location varies depending on the vehicle make and model, often behind the dashboard or in the engine compartment. | |
| Body Control Module (BCM) | Typically located under the dashboard. | |
| Cost to Repair | Low to High | Depends on the cause. Replacing a bulb is inexpensive, while replacing the BCM can be costly. |
| Difficulty Level | Low to Medium | Replacing a bulb or fuse is relatively easy, while diagnosing wiring issues or a faulty BCM can be more complex. |
Detailed Explanations
B2602 Daytime Running Lamp (DRL) Circuit Low (BCM): This code signifies that the Body Control Module (BCM) has detected a voltage level in the DRL circuit that falls below the pre-determined acceptable range. The BCM monitors the voltage to ensure the DRLs are receiving adequate power to illuminate properly.
DRLs not illuminating: This is the most obvious symptom. If the DRLs are not turning on when the vehicle is running and in drive (or a similar automatic activation condition), it suggests a problem within the DRL circuit. This often means the BCM is not sending the signal due to detecting a low voltage issue, or the power isn't reaching the bulbs.
Intermittent DRL operation: Intermittent operation indicates a fluctuating voltage or connection issue. This could be due to loose wiring, a failing relay, or a developing fault within the DRL module (if equipped). The BCM may be detecting dips in voltage that trigger the code and cause the lights to flicker or cut out.
DRLs operating dimly: If the DRLs are illuminated but significantly dimmer than usual, it indicates a restricted flow of power. This can be caused by corrosion in the wiring, a failing relay not providing full voltage, or a partial short circuit drawing power away from the lights.
Warning light illumination: The check engine light or a dedicated DRL warning light on the dashboard may illuminate to alert the driver to a problem with the DRL system. The specific warning light varies by vehicle manufacturer. This is often the first indication that the BCM has detected the B2602 code.
Faulty DRL bulb(s): A burned-out or damaged DRL bulb is a common cause of the B2602 code. When a bulb burns out, it creates an open circuit or significantly increases the resistance, which can result in the BCM detecting a low voltage condition.
Wiring issues: Damaged, corroded, or loose wiring connections can disrupt the flow of electricity to the DRLs. Corrosion increases resistance, while loose connections can cause intermittent voltage drops. Visual inspection is crucial to identify these issues.
Faulty DRL relay: The DRL relay acts as a switch, controlling the flow of power to the DRLs. If the relay is malfunctioning, it may not provide the correct voltage to the circuit, leading to the B2602 code.
Faulty DRL module (if equipped): Some vehicles use a dedicated DRL control module to manage the DRL system. If this module fails, it can send incorrect signals to the BCM or fail to provide adequate power to the DRLs.
Corroded or loose ground connection: A poor ground connection restricts the return path for the electrical current, causing a voltage drop in the circuit. The BCM may interpret this as a low voltage condition, triggering the B2602 code.
Faulty Body Control Module (BCM): While less common, a malfunctioning BCM can incorrectly interpret the voltage in the DRL circuit or fail to send the correct signals. This is usually diagnosed after ruling out other potential causes.
Blown fuse: A blown fuse interrupts the circuit, preventing power from reaching the DRLs. A blown fuse is often a symptom of another problem, such as a short circuit.
Visual inspection: A thorough visual inspection of the DRL bulbs, wiring, and connectors is the first step in diagnosing the B2602 code. Look for signs of damage, corrosion, or loose connections.
Fuse check: Always check the DRL fuse to ensure it is not blown. Replace the fuse if necessary, but be aware that a blown fuse may indicate a more serious problem.
Bulb test: Test the DRL bulbs using a multimeter to confirm they are functioning correctly. You can also swap the bulbs with known good bulbs to see if the problem is resolved.
Wiring continuity test: Use a multimeter to check the continuity of the wiring in the DRL circuit. This will help identify any breaks or open circuits in the wiring.
Voltage drop test: A voltage drop test measures the voltage loss across a specific section of the circuit. Excessive voltage drop indicates high resistance, which can be caused by corrosion or loose connections.
Relay test: Test the DRL relay to ensure it is switching properly and providing the correct voltage to the DRL circuit. You can use a multimeter or a relay tester for this purpose.
Ground connection check: Inspect and clean the ground connection for the DRL circuit. Ensure the connection is secure and free from corrosion.
BCM diagnosis: If all other components check out, the BCM may need to be diagnosed by a qualified technician. This may involve using a scan tool to monitor BCM signals and perform diagnostic tests.
Replace faulty DRL bulb(s): Replacing burned-out or damaged DRL bulbs is a straightforward solution if the bulbs are the cause of the problem.
Repair wiring: Repairing or replacing damaged, corroded, or loose wiring can restore proper electrical flow to the DRLs.
Replace faulty DRL relay: Replacing a malfunctioning DRL relay can resolve issues with intermittent DRL operation or low voltage.
Replace faulty DRL module: Replacing a defective DRL control module (if equipped) can restore proper control over the DRL system.
Clean ground connection: Cleaning and tightening the ground connection for the DRL circuit can improve the flow of electricity and resolve voltage drop issues.
Replace blown fuse: Replacing a blown fuse will restore power to the DRLs, but it's important to address the underlying cause of the blown fuse to prevent it from happening again.
BCM replacement/reprogramming: In rare cases, the BCM may need to be replaced or reprogrammed. This is a more complex repair that should be performed by a qualified technician.
B2600 - Daytime Running Lamp Control Circuit High: This code indicates that the voltage in the DRL circuit is higher than expected.
B2601 - Daytime Running Lamp Control Circuit Range/Performance: This code indicates that the DRL circuit is not performing as expected, but the voltage is not necessarily too high or too low.
B2603 - Daytime Running Lamp Control Circuit Open: This code indicates an open circuit in the DRL circuit, meaning that the electrical path is broken.
Moderate Severity: While the vehicle might still be drivable, inoperative DRLs can compromise safety, especially in low-light conditions. DRLs increase vehicle visibility to other drivers and pedestrians.
Regular inspection of DRLs: Regularly check the DRLs to ensure they are functioning correctly. This will help identify potential problems early on.
Proper wiring maintenance: Keep wiring and connectors clean and free from corrosion. This will help prevent voltage drop and ensure reliable DRL operation.
Multimeter: A multimeter is essential for testing voltage, continuity, and resistance in the DRL circuit.
Wiring diagrams: Wiring diagrams provide a detailed map of the DRL circuit, making it easier to identify and troubleshoot problems.
Socket set/wrenches: Socket sets and wrenches are needed for removing and installing components such as relays and fuses.
Wire stripper/crimper: Wire strippers and crimpers are essential for repairing damaged wiring.
Test light: A test light can be used for quick voltage checks in the DRL circuit.
Location of Components: Understanding the location of the DRL components is crucial for efficient troubleshooting. Refer to your vehicle's repair manual for specific locations.
Cost to Repair: The cost of repairing a B2602 code can vary widely depending on the cause of the problem. Replacing a bulb or fuse is relatively inexpensive, while replacing the BCM can be a costly repair.
Difficulty Level: The difficulty level of repairing a B2602 code can range from low to medium. Replacing a bulb or fuse is a simple task, while diagnosing wiring issues or a faulty BCM can be more complex and require specialized tools and knowledge.
Frequently Asked Questions
What does the B2602 code mean? It means the Body Control Module (BCM) has detected a low voltage condition in the Daytime Running Lamp (DRL) circuit. This often results in the DRLs not working properly.
Can I drive with the B2602 code? Yes, but it's not recommended. Inoperative DRLs can compromise safety, especially in low-light conditions, and may violate local traffic laws.
What are the most common causes of the B2602 code? The most common causes are faulty DRL bulbs, wiring issues, a faulty DRL relay, or a blown fuse. These are relatively easy to check and repair.
How do I fix the B2602 code? Start by visually inspecting the DRL bulbs, wiring, and fuse. Test the bulbs and relay with a multimeter and replace any faulty components.
Do I need a mechanic to fix the B2602 code? Not necessarily. Simple fixes like replacing a bulb or fuse can be done at home. However, more complex issues like wiring problems or a faulty BCM may require professional diagnosis and repair.
Conclusion
The B2602 code indicates a low voltage condition in the DRL circuit, typically detected by the BCM. Proper diagnosis and repair are essential for restoring DRL functionality and ensuring vehicle safety. Always prioritize a systematic approach to troubleshooting, starting with the simplest and most common causes.