Good news! I replaced my AC Delco battery with a RedTop Optima and the Service Column Lock message is gone!

Now I have to find out about that actuator...
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2004 C5 Coupe, 6M, Black, Black/Grey Interior, B&B PRT, TPIS headers, RT X-pipe, Hurst Shifter, full C5 Z06 suspension, Skip Shift Eliminator, Callaway Honker, custom tune.