What does it mean?
B1805 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Manufacturer-Specific Body ECU Fault .
Symptoms
- Several unrelated body functions misbehave at once, such as lighting, locks and wipers
- Warning lamps on the cluster with no obvious mechanical cause
- Intermittent electrical faults that change from one ignition cycle to the next
- The module drops off the network and reappears
- Convenience features stop working until the battery is disconnected and reconnected
Likely causes
- Weak battery or unstable charging voltage causing repeated module resets
- Corroded, loose or undersized body ECU power feed and ground connections
- Water intrusion into the footwell or kick panel where the module is mounted
- Voltage spike from jump starting, a reversed battery connection or welding on the body
- Software or configuration mismatch after a module, key or component replacement
- Internal electronic failure of the body ECU itself
- A short on one of the module output circuits that has damaged an internal driver
How to fix it
- Read every module and record the sub-codes and freeze frame data before clearing anything
- Test the battery and the charging system output under load
- Clean and tighten the body grounds and the module power feed connections
- Check the footwell and kick panel for damp carpet or water tracks
- Clear the codes and note which ones return and in what order
- Check the outputs on the affected circuits for shorts before powering the module again
- Apply an available software update, and only replace and configure the body ECU as the final step