Code Definition

B1939 — Airbag Passenger Pressure Switch Circuit Short To Ground

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

About B1939

B1939 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 B1939 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.

B1939 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 Restraints Control Module (RCM) uses the passenger seat pressure switch to determine whether a passenger is occupying the front seat so it can decide whether to enable or suppress the passenger airbag during a deployment event. DTC B1939 is set when the RCM detects that the pressure switch signal circuit is shorted to chassis ground, producing a stuck low signal that does not change with occupant load. This is commonly caused by chafe damage in the seat track loom where repeated seat travel has worn through the insulation. When this code is active the airbag warning lamp will illuminate an...

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