All 2007-08 RDX trucks, plus 2009 models built from VIN 5J8TB18..9A000001 through 5J8TB18..9A0006069, may turn on the check engine light and store trouble code P1009 (variable valve timing control advance malfunction) in the PCM.
One likely cause, reports Acura, is the control module misinterpreting normal inputs as faults in the VTC system.
Reprogramming the PCM with updated calibration files is the only true fix.
Check with a dealer for the specifics of the flash.