When B1805 appears, the control module has detected abnormal behavior related to Lamp Turn Signal Rear Output Circuit Short To Ground in body electronics and comfort modules.
B1805 Code: Meaning, Symptoms, Causes & Fix
Overview
Symptoms
- battery draw complaints
- related warning lamp illuminated
- module resets or glitches
Common causes
- Disconnected or loose connector affecting lamp turn signal rear output circuit short to ground
- Open circuit in wiring
- Connector pin damage/corrosion or harness stress near related components
How to diagnose B1805
- Confirm B1805 and capture freeze-frame data with a professional scan tool.
- Inspect wiring, connectors, and grounds related to lamp turn signal rear output circuit short to ground for obvious defects.
- Use a continuity test from module pin to component to identify opens/high resistance.
- Check for related DTCs to identify the root-cause chain before replacing parts.
- After repair, clear codes and confirm readiness monitors complete without recurrence.
Severity of code B1805
Moderate: This code is moderate severity: the vehicle may still operate, but fault progression can increase repair cost over time.
Can you drive with B1805?
Most vehicles can be driven short-term with B1805, but postpone heavy load/highway driving until repaired.
If the warning lamp is flashing or drivability/safety is affected, avoid driving and diagnose immediately.
How to fix it (step-by-step)
- Repair obvious wiring/connector faults first to prevent repeat parts replacement.
- Address the root fault mode (open) in the lamp turn signal rear output circuit short to ground circuit/system.
- Apply the required relearn/adaptation procedure if specified by service information.
- Road-test and verify B1805 remains cleared under the conditions that originally set the code.
Fix options
- Repair open circuit and secure connector lock.
- Restore continuity and verify pin tension.
- Clear DTCs and verify with live data and completed drive cycle.
Typical repair cost
$160-$850
Common mistakes when diagnosing B1805
- Replacing parts without verifying voltage, ground, and signal integrity first.
- Ignoring related stored/pending codes that indicate upstream faults.
- Skipping post-repair verification drive cycle and readiness checks.
B1805 in common vehicles
B1805 appears across makes such as Mazda, Subaru, Lexus, Jeep. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.
Frequently asked questions
What causes B1805?
B1805 is commonly set by open faults affecting lamp turn signal rear output circuit short to ground.
How much does it cost to fix B1805?
For B1805, repair costs are typically $160-$850 depending on exact root cause, labor rates, and part quality.
Can I clear B1805 without repair?
You can clear B1805 temporarily, but the code usually returns until the underlying fault is corrected.