Code Definition

B1808 — Lamp Tail Output Circuit Short To Battery

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

About B1808

B1808 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 B1808 is stored, the module has detected a short-circuit (voltage pulled to ground or to supply) in the monitored circuit.

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.

B1808 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 voltage state on the controlled side of the driver to confirm correct operation. DTC B1808 sets when the BCM detects battery voltage on the tail lamp output line at a time when the lighting switch is off and the line should be at 0V or floating, indicating that the wiring or load has shorted to a battery feed somewhere between the BCM driver and the lamp ground. The most common cause on combination tail lamp assemblies is a corroded dual filament bulb base bridging the always live battery feed (where one is present) o...

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