B1802: Lamp Turn Signal Rear Output Circuit Failure

Definition

The OBD2 code B1802 indicates a malfunction in the rear turn signal output circuit, suggesting a failure in the circuit responsible for activating the rear turn signal lights

Common causes

Faulty turn signal bulb
Damaged wiring or connectors
Short circuit in the circuit
Open circuit in the circuit
Faulty turn signal relay
Malfunctioning body control module (BCM)
Corroded or loose connections
Faulty ground connection

Common misdiagnoses

Faulty turn signal bulb
Bad turn signal switch
Damaged wiring or connectors
Faulty body control module (BCM)
Incorrectly installed or loose bulb socket
Grounding issues
Faulty relay
Corroded terminals

Troubleshooting steps

1. Visual Inspection
2. Check the rear turn signal bulbs for any signs of damage or burnout. Replace any faulty bulbs
3. Inspect the bulb sockets for corrosion, dirt, or damage. Clean or replace as necessary
4. Examine the wiring and connectors leading to the rear turn signal for any signs of fraying, breaks, or corrosion
5. Check Fuses
6. Locate the fuse box and check the fuses related to the turn signal circuit. Replace any blown fuses
7. Test the Turn Signal Switch
8. The turn signal switch on the steering column can sometimes fail. Test the switch for proper operation using a multimeter or by checking for continuity
9. Use a Multimeter
10. With the turn signal activated, use a multimeter to check for voltage at the turn signal socket. If there is no voltage, trace the wiring back to the turn signal switch and check for continuity
11. Check for ground at the turn signal socket. A poor ground connection can cause the circuit to fail
12. Inspect the Body Control Module (BCM)
13. The BCM controls various lighting functions, including turn signals. If all other components check out, the BCM may be faulty. Use a scan tool to check for any additional codes or issues related to the BCM
14. Check for Short Circuits
15. Inspect the wiring for any signs of short circuits, especially in areas where the wiring may rub against metal or other components
16. Clear Codes and Test
17. After performing repairs, clear the OBD-II codes using a scan tool and take the vehicle for a test drive to see if the code returns
18. Consult Wiring Diagrams
19. If the issue persists, consult the vehicle’s wiring diagrams to trace the circuit and identify any other components that may be involved
20. Professional Diagnosis
21. If you are unable to resolve the issue after these steps, consider seeking help from a professional mechanic who can perform more advanced diagnostics. By following these steps, you should be able to identify and resolve the issue related to the B1802 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Visual Inspection

2. Check the rear turn signal bulbs for any signs of damage or burnout. Replace any faulty bulbs

3. Inspect the bulb sockets for corrosion, dirt, or damage. Clean or replace as necessary

4. Examine the wiring and connectors leading to the rear turn signal for any signs of fraying, breaks, or corrosion

5. Check Fuses

6. Locate the fuse box and check the fuses related to the turn signal circuit. Replace any blown fuses

7. Test the Turn Signal Switch

8. The turn signal switch on the steering column can sometimes fail. Test the switch for proper operation using a multimeter or by checking for continuity

9. Use a Multimeter

10. With the turn signal activated, use a multimeter to check for voltage at the turn signal socket. If there is no voltage, trace the wiring back to the turn signal switch and check for continuity

11. Check for ground at the turn signal socket. A poor ground connection can cause the circuit to fail

12. Inspect the Body Control Module (BCM)

13. The BCM controls various lighting functions, including turn signals. If all other components check out, the BCM may be faulty. Use a scan tool to check for any additional codes or issues related to the BCM

14. Check for Short Circuits

15. Inspect the wiring for any signs of short circuits, especially in areas where the wiring may rub against metal or other components

16. Clear Codes and Test

17. After performing repairs, clear the OBD-II codes using a scan tool and take the vehicle for a test drive to see if the code returns

18. Consult Wiring Diagrams

19. If the issue persists, consult the vehicle’s wiring diagrams to trace the circuit and identify any other components that may be involved

20. Professional Diagnosis

21. If you are unable to resolve the issue after these steps, consider seeking help from a professional mechanic who can perform more advanced diagnostics. By following these steps, you should be able to identify and resolve the issue related to the B1802 code