Code P103, Open Brake Booster Vacuum (BBV) Sensor: Notes
WARNING: This page is about a different car, the 1995 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
Brake booster vacuum sensor changes resistance based on vacuum inside brake booster. This test checks for a vacuum reading which can be caused by an open sensor or open on circuit No. 474 or and short to ground on circuit No. 1726. When PCM detects as brake booster vacuum signal that is too low, Code P103 will set.