HELP! Received OBD Code P0508 - Idle Control System Circuit Low

Anyone ever receive this code from a OBD code reader? What does it mean? What is the required repair, if any he says in a hopeful voice.
Any adive would be greatly appreciated, thanks
Patrick
Some background: Recently purchased this 2002 Durango (SLT, 4.7) with 23,000 miles. I have had the truck for about three weeks and last night reversing out of a driveway (with a hill, parked up hill) it stalled as I shifted it from Reverse to Drive. Soon after this I stopped and filled the gas tank, as I left the gas station and entered the highway it stalled again and the engine light came on. Truck restarted and light stayed on for the one hour drive home. Rough idle all the way home. Once I got home and restarted the D several times, engine light went out, as expected. Based on a suggestion from this site (thank you) went to Harbor Freight and picked up a $40 OBD Code Reader, which indicated the above code. This is my first used car purchase and starting to regret it a little.
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