DIAGNOSIS You want to perform a factory reset on the opener's learned codes, usually because you lost a remote or moved into a new house.
FIX On the B2405 motor unit itself, you'll find a rectangular 'Learn' button, usually colored yellow, orange, or purple. 1) Press and hold that Learn button for about 10 seconds. You'll see the indicator light next to it go out. 2) Release the button. This erases all learned remotes and keypads from its memory. The door will not operate from any previous wireless device now. 3) To reprogram your devices, press the Learn button once briefly—the light will come on solid. Then, within 30 seconds, press the button on the remote you want to add. The opener light will flash to confirm. Repeat for each remote and keypad.
IF THAT DIDN'T WORK If the old remote still works after this, someone might have programmed it using the older, fixed-code DIP switches (if your model has them). Check for a small compartment on the back of the remote and inside the opener's light cover for a set of tiny switches. If present, you need to physically change the switch pattern on the remote to match the opener, or vice-versa.
HEADS UP Remember to reprogram any wall-mounted keypads and your car's HomeLink system after the reset, as they are erased too. Write down the new Learn button color/code for future reference.