Check engine light should light up when you turn the key on...before you start the engine. <img src="/forums/images/graemlins/wink.gif" alt="" />

I'd still lean towards the engine coolant temperature sensor...this is the one the ECU uses...not the temp gauge sensor. <img src="/forums/images/graemlins/wink.gif" alt="" />

Where does yer temp gauge needle sit when the engine is warmed up? Is the thermostat working correctly? How long does it take fer the engine to come to operating temperature?

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