that system was known for the type of trouble you are having. I'd vote it is probably not the bulb, but rather the sensor in the passenger seat. It seems to mistakenly be sensing pressure on the seat, where there is none. Maybe an adjustment?

Scott B. "I'm a self-made man... I started with nothing, and I still have most of it!" 68 360 rusty B'cuda 'vert (GO Fish)13.59@ 98.72 mph 69 340 GTS stock 14.18@ 95.60 mph 01 5.9L Ram 1500 Quad Cab 4x4 01 3.5L 300M 16.23@ 86.97 mph