There are basically 3 items in the system; the bulb, the igniter, and the ballast. In this situation, I usually recommend swapping parts side to side to determine the defective part. You'll have to remove the front bumper cover to do so (which is pretty easy), and it will involve an hour or two of work, but in the end, it'll save you easily $100-$200 in parts replacement cost in chasing the issue.
Tim Poliniak - ASE Certified Parts Specialist, 18 years with Acura/Honda
Acura of Peoria ~ www.oemacuraparts.com