Code Definition

B1806 — Lamp Tail Output Circuit Failure

System: Body  |  Type: Manufacturer-Specific  |  Make: Generic

About B1806

B1806 is a manufacturer-specific body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1806 is stored, the module has detected an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

B1806 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The Body Control Module (BCM) controls the tail lamp output and monitors the circuit for proper operation by measuring current draw and feedback voltage when the tail lamps are commanded on with the parking lights or headlights. DTC B1806 sets when the BCM detects an electrical fault on the tail lamp output, such as an open circuit, short to ground, or short to battery, that prevents the lamps from operating within expected parameters. Tail lamps run continuously while the lighting switch is on rather than flashing like turn signals, and are typically driven through a single BCM output that fe...

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