OBD-II Fault Code

B1806: Lamp Tail Output Circuit Failure

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for B1806.

System family

Body

Manufacturer-specific

Repair category

Lighting

Use this category to narrow your checks before replacing parts.

Severity

Medium

Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.

What B1806 usually means

Lamp Tail Output Circuit Failure.

Common symptoms

Body/accessory warning lamp or feature not working

Likely causes

Blown bulb/LED module; Poor ground; Fuse/relay fault; Switch/module/wiring issue

Diagnostic checks

Check related fuses, connectors, grounds and switch/module power supply; Check bulb/module, fuse, ground and connector corrosion

Repair guidance

Replace failed bulb/module, repair ground/wiring, replace switch/relay if confirmed

Verification after repair

Operate the affected body/accessory system and rescan

Note: Confirm vehicle make/model/year because manufacturer-specific codes can vary; Manufacturer-specific: confirm definition and test steps in the vehicle service manual. A DTC identifies a circuit or system condition, not always the failed part.