B1804
Low Severity (Level 1)Lamp Turn Signal Rear Output Circuit Short To Battery
B1804 usually means lamp Turn Signal Rear Output Circuit Short To Battery.
Can you still drive with B1804?
✅Safe to drive — this is an informational or minor issue. Schedule diagnosis at your convenience.
Typical repair cost: $10 – $200
Severity Level 1 — Low
This code indicates a minor issue that is unlikely to cause immediate driveability problems. You can typically continue driving but should have the vehicle inspected at your earliest convenience.
Common Symptoms
- Battery draining overnight or when vehicle is parked
- Turn signals not responding to controls — stuck in one state
- Turn signals staying on or functioning when they shouldn't (powered continuously)
- Excessive current draw on the turn signal/hazard system circuit (fuse may blow repeatedly)
Possible Causes
- Damaged wiring in the turn signal/hazard system harness shorted to a 12V power source — wiring insulation chafed through from rubbing against metal body panels
- Water intrusion or corrosion in turn signal/hazard system electrical connector causing internal short to battery voltage
- Failed turn signal flasher — internal short to power within the component
- Aftermarket accessory installation tapped into the wrong circuit, back-feeding 12V
Common Fixes
- Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($12-112 at shop, free at auto parts store for basic scan)
- Visually inspect the turn signal/hazard system wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $104 diagnostic fee at shop)
- Repair or replace damaged section of wiring harness where short is located — solder and heat-shrink all connections, don't use crimp connectors on critical circuits ($177-312 depending on accessibility)
- If turn signal flasher is internally shorted, replace with a quality OEM or OEM-equivalent aftermarket unit ($10-200)
- Clean all ground points related to the turn signal/hazard system — remove bolt, sand contact surface to bare metal, apply dielectric grease, and torque to spec ($59-198 at shop)
Estimated Repair Cost
These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.
Frequently Asked Questions
What does B1804 mean?
B1804 stands for "Lamp Turn Signal Rear Output Circuit Short To Battery". B1804 usually means lamp Turn Signal Rear Output Circuit Short To Battery.
Can you drive with B1804?
Safe to drive — this is an informational or minor issue. Schedule diagnosis at your convenience.
How much does it cost to fix B1804?
Repair costs for B1804 typically range from $10 to $200, depending on your vehicle make, model, and local labor rates. Common fixes include: Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($12-112 at shop, free at auto parts store for basic scan); Visually inspect the turn signal/hazard system wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $104 diagnostic fee at shop); Repair or replace damaged section of wiring harness where short is located — solder and heat-shrink all connections, don't use crimp connectors on critical circuits ($177-312 depending on accessibility).
Will B1804 clear itself?
Related Repair Costs
Explore Repair Costs
Related OBD-II Codes
These codes are in the same range as B1804 and often share similar causes and fixes.
Worried about repair costs?
Get transparent estimates and verify your mechanic's quote before authorizing repairs.
Related Discussions
See what other car owners are saying about this code and related repairs.
View B1804 discussions in the community