Code Definition

B1738 — Mirror Driver Horizontal Switch Circuit Open

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

About B1738

B1738 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 B1738 is stored, the module has detected an open (broken or disconnected) electrical path 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.

B1738 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 circuit, which is the line that carries the switch state back to the module when the driver presses the mirror selector left or right. DTC B1738 is set when the module detects an open circuit on this input line, meaning the signal path between the switch and the module is broken or the switch contact is failing to make. The module expects to see a defined voltage or resistance value when the switch is operated, and an open results in either no signal change or a steady hig...

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