Probably the sensor located at the top of the reservoir. I had mine topped as high as it would go and it would slowly fade in and out. I just unplugged it and check my fluids daily.

I guess you could replace yers as well...not sure how much they cost though.

Did you check the wiring on the parking brake switch? <img src="/forums/images/graemlins/wink.gif" alt="" />

1998 T-100 Xtra cab SR5 2WD Auto; Roadmaster Active Suspension; Yokohama Geolander HT-S; lowered air dam; full belly pan; 4? diffuser; 11" side skirts; dual transmission coolers; 67% grill blocked; Auto-RX'd; ScanGauge II/Ultra-Gauge