Code Definition

B1878 — Seatbelt Driver Pretensioner Circuit Short to Battery

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

About B1878

B1878 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 B1878 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.

B1878 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

B1878 is set by the Restraints Control Module (RCM) when it detects that the driver side seat belt pretensioner squib circuit is shorted to a voltage source, most commonly battery positive, anywhere between the RCM output pin and the pretensioner squib. The RCM monitors both squib leads independently for unintended voltage and immediately latches this code if either lead measures pulled up to a non zero potential when the circuit should be floating. The pretensioner is a pyrotechnic device built into the driver seat belt retractor or buckle that fires during a crash to remove slack from the be...

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