Product review (5 stars): Easy fix for an ice maker that quit working
This kit has the two circuit boards needed to replace the left and right side icemaker optics in applicable KitchenAid/Whirlpool side-by-side refrigerators.  My 7-year-old icemaker quit, and it turns out this is the only repair kit I needed to restore its functionality.

Replacement of the two optics boards took about five minutes: three screws on each side of the freezer compartment, disconnect and remove the optics panels, remove the screws holding the circuit boards in place (one on the left panel, two on the right panel), remove the circuit boards, and reassemble with the new boards by reversing the process.  You can watch this step-by-step process online -- just search on YouTube for the part number, 4389102.

The kit also supplies a wiring diagram and diagnostic instructions for the new circuit boards, and a suggestion where to save them in the base plate of the refrigerator along with the other diagrams stored there.

I have had this optics kit installed since June 29, 2012.  The icemaker has been functioning like new since then.

So how do you know if you need to replace the optics?  Do a diagnostic test:

Check that the icemaker on/off switch (right side of freezer compartment) is ON.  Look at the red status light next to the on/off switch.  You should see the flight flash twice and repeat the double-flash every second.  Now close the left side flapper and don't block the light path from the right side where the red status light is.  The red status light should stop flashing and come on steady. If it is still flashing, your optics may be blocked -- or they might be bad, like mine were.  You might want to wait 5 minutes then unplug the refrigerator for 10 seconds to reset the ice maker control board and try the diagnostic again.

If the light still won't come on steady, you can check the rest of the icemaker by bypassing the optics system.  USE CAUTION, as the optics connections are live -- unplug the refrigerator for safety while bypassing the system.  First remove the right side optics panel (3 screws).  Next, disconnect the cable plug from the refrigerator going to the optics panel.  Now jump 2 specific connections on the refrigerator's plug (I cut a large paper clip and insulated the middle for this purpose).  The correct 2 wires to jump are next to each other and may be identified by color: black, and black-with-white.  Turns out my model used different colors, but I found online that the correct wires can be identified as the ones immediately below the bottom-most hole on the plug where no wire is connected (there are 4 wires next to each other filling up the rest of the plug below the hole).  I found a description and photos of this bypass operation on the ApplianceJunk (Appliance Repair Help) website by Googling the three words: 4389102 jumper paperclip (4389102 is the part number of this optics kit).  If the only thing wrong with your icemaker was the optics system, your icemaker will eventually make ice again (24 hours or less -- mine took about 2 hours).  Note: once the icemaker starts, it won't stop making ice while the jumper is in place, so don't let the icemaker keep going too long or it will overfill the bin and cause problems!