OBD Guide

B1804

Lamp Turn Signal Rear Output Circuit Short To Battery

B1804 is an OBD-II diagnostic trouble code meaning: Lamp Turn Signal Rear Output Circuit Short To Battery. Common causes: damage to wire insulation, short circuit in wiring harness. Estimated repair cost: $6–56.

Severity
⚠️ Medium
Can you drive?
Do not drive — repair immediately
Approx. repair cost
$6–56 (est.)

Symptoms

  • Rear turn signals do not work
  • Flashing of indicators at an abnormal frequency
  • The fault light on the instrument panel is on

Causes

  • Damage to wire insulation
  • Short circuit in wiring harness
  • Turn signal relay malfunction
  • Corrosion of contacts in the rear light
  • Problems with the control unit

How to Fix

  1. Conduct a visual inspection of the wires and harness in the rear light area
  2. Check the continuity of the circuit with a multimeter
  3. Replace damaged wires or electrical tape
  4. Clean the contacts in the rear light
  5. Check and, if necessary, replace the turn signal relay
  6. Flash or replace the control unit if necessary

Related codes

FAQ

What does the B1804 code mean?

B1804 is an OBD-II diagnostic trouble code that indicates: Lamp Turn Signal Rear Output Circuit Short To Battery

What causes a B1804 error code?

The most common causes of B1804 include: Damage to wire insulation; Short circuit in wiring harness; Turn signal relay malfunction; Corrosion of contacts in the rear light.

How do I fix a B1804 diagnostic trouble code?

To fix B1804: Conduct a visual inspection of the wires and harness in the rear light area. Check the continuity of the circuit with a multimeter. Replace damaged wires or electrical tape. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with B1804?

Do not drive — repair immediately

How much does it cost to fix B1804?

The estimated repair cost for B1804 is $6–56. Actual cost depends on your vehicle, location, and labor rates.

See also: Russian version · NationStat