Sounds like a ground problem but before digging into that have you verified BOTH of your battery cables are tight and making good contact? Also that they are not only tight but the inserts they screw into on the battery are not loose in the battery even though the cables are tight in them? I've had both problems and they'll do some really wonky things to the cluster and gauges and sensors. This is a common s-10 problem.
2001 CC LS, pewter, stock, 4.3,Wait4meperformance, CFM throttle blade, Helix throttle body spacer, 4spd auto, 3button electric 4x4 shift, heavy duty factory suspension, Bilsteins, 1" rear wheel spacers, skid plates.