Test F: Left PRETENSIONER Circuit Short To Battery Or Ignition (DTC B1878): Description
WARNING: This page is about a different car, the 2002 Ford Pickup, 2002 Ford F550 Super Duty, 2002 Ford F450 Super Duty, 2002 Ford Excursion, and 2002 Ford Cab & Chassis. 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.