Code Definition

B1778 — Mirror Driver Down Circuit Failure

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

About B1778

B1778 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 B1778 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.

B1778 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 or Driver Door Module monitors the driver side power mirror motor circuits, including the down direction drive output. DTC B1778 sets when the module detects an electrical fault on the mirror down movement circuit, such as an open circuit, short to ground, short to power, or excessive current draw when the down command is active. The mirror motor is a small reversible DC motor driven through H bridge outputs from the module, with the polarity of supply reversed to change movement direction. When this code is set, the driver mirror may fail to tilt downward, move erratic...

Join TaT to view the complete code information and diagnostic details.

Quick Facts