Here are the steps I took:
1. CDP: AAA code (look up your club number for the discount). Mine is "14".
2. PC: 135892 (Promotional Coupon)
3. RQ: FRDM (Rate Code)
HTH!
Update: I do most rentals at the HLE. This did not work at the APO on an upcoming trip. I only did steps 1 and 2 OR 1 and 3 for about the same cost $30.xx w/taxes.