B1802 Lamp Turn Signal Rear Output Circuit Failure

Introduction

The B1802 diagnostic trouble code (DTC) signifies a malfunction within the rear turn signal output circuit. This fault can lead to the rear turn signal not functioning correctly, posing a safety risk and potentially resulting in legal repercussions. Understanding the causes, symptoms, and troubleshooting steps associated with B1802 is crucial for effective diagnosis and repair. This article provides a comprehensive overview of the B1802 code, covering its possible causes, symptoms, diagnostic procedures, and potential solutions.

Comprehensive Table

Category	Description	Potential Impact
Definition	B1802: Lamp Turn Signal Rear Output Circuit Failure. Indicates an electrical issue in the circuit controlling the rear turn signal lamp.	Malfunctioning or non-functional rear turn signal. Increased risk of accidents due to lack of clear signaling. Potential fines and legal issues for operating a vehicle with defective safety equipment.
Possible Causes	Faulty Turn Signal Bulb: Burned-out or damaged bulb. Wiring Issues: Short circuits, open circuits, corrosion, or damage to wiring harness. Connector Problems: Loose, corroded, or damaged connectors in the circuit. Faulty Turn Signal Switch: Internal failure in the switch preventing proper signal transmission. Faulty Body Control Module (BCM): Internal failure in the BCM output circuit responsible for the rear turn signal. Fuse Issues: Blown fuse related to the turn signal circuit.	Intermittent or complete failure of the rear turn signal. Difficulty in diagnosing the root cause of the problem. Potential damage to other electrical components due to short circuits. Increased risk of electrical fires.
Symptoms	Rear turn signal lamp not illuminating. Rear turn signal lamp illuminating dimly or intermittently. Hyper-flashing (rapid blinking) of the turn signals on the affected side (and potentially on the instrument panel). Error message or warning light on the dashboard related to turn signal malfunction. * Other electrical issues, such as problems with other lights controlled by the BCM.	Misleading or absent turn signals, increasing the risk of accidents. Frustration and inconvenience for the driver. Potential safety inspection failure. Difficulty in selling or trading in the vehicle due to the known electrical issue.
Diagnostic Steps	1. Visual Inspection: Check the turn signal bulb for damage. Examine wiring and connectors for any signs of damage, corrosion, or loose connections. 2. Fuse Check: Inspect the fuse related to the turn signal circuit and replace if blown. 3. Bulb Test: Replace the turn signal bulb with a known good bulb to rule out bulb failure. 4. Voltage Test: Use a multimeter to check for proper voltage at the turn signal bulb socket. 5. Continuity Test: Use a multimeter to check for continuity in the wiring between the turn signal switch, BCM, and bulb socket. 6. Scan Tool Diagnosis: Use an OBD-II scan tool to retrieve any other related DTCs and to monitor BCM output signals. 7. BCM Testing: If other components check out, suspect a faulty BCM. BCM testing might require specialized equipment and expertise.	Time-consuming troubleshooting process. Potential for misdiagnosis if proper procedures are not followed. Need for specialized tools and equipment, increasing the cost of repair. Necessity of consulting a qualified technician for complex diagnostic procedures.
Possible Solutions	Replace the faulty turn signal bulb. Repair or replace damaged wiring or connectors. Replace the faulty turn signal switch. Replace the faulty BCM (requires programming). Repair short circuits or open circuits in the wiring harness. Clean corroded connectors. * Replace blown fuse.	Restoration of proper turn signal functionality. Improved safety and reduced risk of accidents. Compliance with traffic laws and regulations. Increased value and reliability of the vehicle.
Related DTCs	B1801 (Lamp Turn Signal Front Output Circuit Failure), B1803 (Lamp Turn Signal Side Output Circuit Failure), B1804 (Lamp Turn Signal Ground Circuit Failure), other B-codes related to lighting and body control systems.	Potential interaction between different lighting circuits, making diagnosis more complex. Need to consider other potential electrical issues that may be contributing to the problem. Possible misdiagnosis if related DTCs are not properly investigated.
Tools & Equipment Needed	Multimeter, OBD-II scan tool, wiring diagrams, circuit tester, socket set, pliers, wire stripper, wire crimper, replacement bulbs, fuses, connectors, and wiring.	Financial investment in tools and equipment. Need for proper training and knowledge to use the tools effectively. Potential for injury if tools are not used safely.
Safety Precautions	Disconnect the negative battery terminal before working on the electrical system. Use proper personal protective equipment (PPE) such as gloves and safety glasses. Refer to the vehicle's service manual for specific wiring diagrams and procedures. Avoid working on the electrical system in wet or damp conditions.	Prevention of electrical shock and injury. Protection of the vehicle's electrical system from damage. Ensuring accurate and safe diagnostic and repair procedures.

Detailed Explanations

Definition: The B1802 code is a specific diagnostic trouble code (DTC) that indicates a malfunction within the rear turn signal output circuit. This means the vehicle's computer has detected an electrical problem affecting the circuit that controls the rear turn signal lamp, preventing it from functioning correctly. This could stem from a variety of issues ranging from a simple blown bulb to a complex wiring problem or a faulty control module.

Possible Causes:

Faulty Turn Signal Bulb: A burned-out or damaged bulb is the most common cause of a turn signal failure. The filament inside the bulb may have broken, preventing it from illuminating.
Wiring Issues: Damaged or corroded wiring can interrupt the flow of electricity to the turn signal bulb. This can include short circuits, where the wire is inadvertently connected to ground, or open circuits, where the wire is completely broken.
Connector Problems: Connectors are used to join different parts of the electrical circuit. If these connectors are loose, corroded, or damaged, they can prevent electricity from flowing properly.
Faulty Turn Signal Switch: The turn signal switch, usually located on the steering column, controls the activation of the turn signals. A faulty switch can prevent the signal from being sent to the rear turn signal lamp.
Faulty Body Control Module (BCM): The BCM is a computer that controls various electrical functions in the vehicle, including the turn signals. A faulty BCM can prevent the rear turn signal from working.
Fuse Issues: A blown fuse is a safety device that protects the electrical circuit from overcurrent. If the fuse related to the turn signal circuit is blown, it will prevent the rear turn signal from working.

Symptoms:

Rear turn signal lamp not illuminating: This is the most obvious symptom of a B1802 code. The rear turn signal lamp will not light up when the turn signal is activated.
Rear turn signal lamp illuminating dimly or intermittently: The rear turn signal lamp may light up, but it may be very dim or it may flicker on and off.
Hyper-flashing (rapid blinking) of the turn signals: When a turn signal bulb is not working, the remaining turn signals on that side of the vehicle may blink rapidly. This is a warning that one of the bulbs has failed.
Error message or warning light on the dashboard: Some vehicles have a warning light or message on the dashboard that will illuminate when a turn signal bulb is not working.
Other electrical issues: In some cases, a B1802 code may be accompanied by other electrical issues, such as problems with other lights controlled by the BCM.

Diagnostic Steps:

Visual Inspection: Begin by visually inspecting the turn signal bulb for any signs of damage, such as a broken filament. Also, inspect the wiring and connectors for any signs of damage, corrosion, or loose connections.
Fuse Check: Locate the fuse related to the turn signal circuit in the vehicle's fuse box. Use a fuse tester or multimeter to check if the fuse is blown. If it is, replace it with a new fuse of the same amperage rating.
Bulb Test: Replace the turn signal bulb with a known good bulb to rule out bulb failure. If the new bulb works, then the original bulb was the problem.
Voltage Test: Use a multimeter to check for proper voltage at the turn signal bulb socket. With the turn signal activated, you should see approximately 12 volts at the socket. If there is no voltage, then there is a problem with the wiring or the BCM.
Continuity Test: Use a multimeter to check for continuity in the wiring between the turn signal switch, BCM, and bulb socket. This will help to identify any open circuits in the wiring. Disconnect the battery before doing this.
Scan Tool Diagnosis: Use an OBD-II scan tool to retrieve any other related DTCs and to monitor BCM output signals. This can provide valuable information about the problem.
BCM Testing: If all other components check out, suspect a faulty BCM. BCM testing might require specialized equipment and expertise. A professional technician should perform this test.

Possible Solutions:

Replace the faulty turn signal bulb: If the bulb is burned out or damaged, replacing it will solve the problem.
Repair or replace damaged wiring or connectors: If the wiring or connectors are damaged, they need to be repaired or replaced. This may involve soldering wires together or replacing the entire wiring harness.
Replace the faulty turn signal switch: If the turn signal switch is faulty, it needs to be replaced.
Replace the faulty BCM (requires programming): If the BCM is faulty, it needs to be replaced. Replacing the BCM often requires programming the new module to match the vehicle's specific configuration. This is usually done by a qualified technician.
Repair short circuits or open circuits in the wiring harness: This involves identifying and repairing the source of the short circuit or open circuit.
Clean corroded connectors: Clean corroded connectors with a wire brush or contact cleaner.
Replace blown fuse: Replace a blown fuse with a new fuse of the same amperage rating.

Related DTCs:

B1801 (Lamp Turn Signal Front Output Circuit Failure): Indicates a malfunction in the front turn signal output circuit.
B1803 (Lamp Turn Signal Side Output Circuit Failure): Indicates a malfunction in the side turn signal output circuit.
B1804 (Lamp Turn Signal Ground Circuit Failure): Indicates a problem with the ground connection for the turn signal circuit.
Other B-codes related to lighting and body control systems: These codes can provide additional information about the vehicle's electrical system and may be related to the B1802 code.

Tools & Equipment Needed:

Multimeter: Used to measure voltage, current, and resistance in the electrical circuit.
OBD-II scan tool: Used to retrieve diagnostic trouble codes from the vehicle's computer.
Wiring diagrams: Used to understand the vehicle's electrical system and locate specific wires and components.
Circuit tester: Used to test for voltage and continuity in the electrical circuit.
Socket set, pliers, wire stripper, wire crimper: Used to repair and replace wiring and connectors.
Replacement bulbs, fuses, connectors, and wiring: Used to replace faulty components.

Safety Precautions:

Disconnect the negative battery terminal: This will prevent electrical shock and damage to the vehicle's electrical system.
Use proper personal protective equipment (PPE): Wear gloves and safety glasses to protect yourself from electrical shock and other hazards.
Refer to the vehicle's service manual: The service manual contains specific wiring diagrams and procedures for your vehicle.
Avoid working on the electrical system in wet or damp conditions: Water can conduct electricity and increase the risk of electrical shock.

Frequently Asked Questions

What does the B1802 code mean? The B1802 code signifies a Lamp Turn Signal Rear Output Circuit Failure, indicating a problem within the electrical circuit controlling the rear turn signal lamp.

What are the most common symptoms of a B1802 code? The most common symptom is a rear turn signal lamp that doesn't illuminate. Other symptoms include dim or intermittent illumination, and hyper-flashing of the turn signals.

Can I fix the B1802 code myself? Depending on your mechanical skills, you might be able to fix it. Start with simple checks like the bulb and fuse, but complex wiring or BCM issues might require a professional.

What if replacing the bulb doesn't fix the problem? If a new bulb doesn't fix the issue, there may be an issue with the wiring, the connector, the switch, or even the BCM. Further diagnosis is necessary.

Is it safe to drive with a B1802 code? Driving with a malfunctioning turn signal is unsafe and potentially illegal. Get it fixed as soon as possible to avoid accidents.

Conclusion

The B1802 DTC signals a fault in the rear turn signal output circuit, potentially arising from bulb failures, wiring problems, or BCM issues. Proper diagnosis and repair are crucial for safety and legal compliance; therefore, a thorough inspection and, if needed, professional assistance are highly recommended.