Test F: Left PRETENSIONER Circuit Short To Battery Or Ignition (DTC B1878): Description
WARNING: This page is about a different car, the 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, and 2004 Ford Excursion. However, it is still accessible from the selected car via links, so may be relevant.
Restraints Control Module (RCM) monitors circuits to left seat belt pretensioner. When RCM detects a circuit short to battery or ignition, it will store Diagnostic Trouble Code (DTC) B1878 in memory and flash Code 17 on AIR BAG warning light.