B1804: Lamp Turn Signal Rear Output Circuit Short To Battery
MediumBodyLighting
What does B1804 mean?
B1804 is a diagnostic trouble code indicating "Lamp Turn Signal Rear Output Circuit Short To Battery". The ECU is detecting a voltage reading that is below the expected range in the lighting circuit. This typically points to a wiring short, a faulty sensor, or a grounding issue.
Common causes
- Damaged or corroded wiring harness
- Loose or disconnected electrical connector
- Failed lighting sensor or actuator
- Blown fuse in the related circuit
- Poor ground connection
What should you do?
Schedule a diagnostic appointment at your earliest convenience. The vehicle is generally safe to drive short distances, but the underlying issue should be addressed to prevent it from worsening.
Get a diagnosis for YOUR car
Code B1804 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.