Code Definition

B1739 — Mirror Driver Horizontal Switch Circuit Short To Battery

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

About B1739

B1739 is a manufacturer-specific body diagnostic trouble code recorded for Ford vehicles. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1739 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.

B1739 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 Driver Door Module (DDM) or Body Control Module (BCM) monitors the driver side exterior mirror horizontal switch input line, which carries the switch state from the mirror selector back to the module. DTC B1739 is set when the module detects an unexpected battery voltage on this input circuit, indicating a short to power somewhere between the switch and the module. The expected reading on this input is a low signal voltage or a defined resistance to ground that changes when the switch is operated, so a steady high voltage indicates the wire has come into contact with a live source. When th...

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