OBD2 Car ScannerWhat does B1804 mean?
B1804 stands for Lamp Turn Signal Rear Output Circuit Short To Battery. A body control module has found a fault in a comfort or safety system such as airbags, lights, doors, seats or climate control.
Body codes cover the airbags, seats, lights, doors and comfort systems. When the car's computer sees a reading outside its normal range, it stores this code and may turn on a warning light on the dashboard.
Common causes
- Damaged wiring or a loose connector (often under seats)
- Faulty switch, sensor or motor
- Low battery voltage
- Faulty body control module
What to do
- Read all stored and pending codes with a scanner. Several codes together often point to one cause.
- Note the freeze frame data (speed, temperature, load) recorded when the code was set.
- Inspect the wiring and connectors of the part named in the code for damage, corrosion or looseness.
- Fix the most likely and cheapest cause first, then clear the code and drive to see if it comes back.
Read this code from your own car
Plug in a cheap ELM327 adapter and the app shows every fault code, what it means and how to fix it.
Frequently asked questions
What does B1804 mean?
B1804 means “Lamp Turn Signal Rear Output Circuit Short To Battery”. It belongs to the body system group: A body control module has found a fault in a comfort or safety system such as airbags, lights, doors, seats or climate control.
Is it safe to drive with B1804?
You can usually drive carefully for a short time, but fix it soon to avoid further damage or higher fuel use.
How do I clear B1804?
Fix the cause, then clear the code with an OBD2 scanner or app. If the fault is still there, the code will come back.
Related codes
- B1800Lamp Turn Signal Front Output Circuit Short To Battery
- B1801Lamp Turn Signal Front Output Circuit Short To Ground
- B1802Lamp Turn Signal Rear Output Circuit Failure
- B1803Lamp Turn Signal Rear Output Circuit Open
- B1805Lamp Turn Signal Rear Output Circuit Short To Ground
- B1806Lamp Tail Output Circuit Failure
- B1807Lamp Tail Output Circuit Open
- B1808Lamp Tail Output Circuit Short To Battery
Code meanings can vary by manufacturer. This page is general guidance, not a repair manual. Always confirm the cause before replacing parts.