Code Definition

B1800 — Lamp Turn Signal Front Output Circuit Short To Battery

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

About B1800

B1800 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 B1800 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.

B1800 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 front turn signal lamp output and monitors the voltage state on the controlled side of the driver when the lamp is commanded off. DTC B1800 sets when the BCM detects battery voltage on the front turn signal output line at a time when that line should be at 0V or floating between flash pulses, indicating that the wiring or load has shorted to a battery feed somewhere between the BCM driver and the lamp ground. To prevent damage to the internal switching transistor, the BCM typically disables the output once the short is detected. When this code is set,...

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