I guess you can pull the plugs/wires and check them over. You can measure the wires and see what resistance values they are reading.

I'd still recommend gitting one of those diagnostics doodads...better than throwing parts at the problem trying to fix it. <img src="/forums/images/graemlins/smile.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