new Idle Control Valve installed. still get P1506

disconnected the battery engine light came back on in 40 miles idle is ok..no smoke

Check wires/connector to IAC. Try cleaning T-body and back side of the throttle plate as well with a toothbrush and flush with clearner, clean IAC passages as well. Start engine to purge cleaner and warm up to operating temp. Disconnect battery for at least 20 min. to reset KAM. Or (keep alive memory)