Eureka! Problem solved at last! If you have a 2004-2007 non-SKS (Smart Key System) Prius and you're trying to make a new or used fob work with your car, I finally found the answer. Lots of people have been asking about how to do this for a long time but all of the directions I've found were slightly incorrect. Again, my directions have only been tested on a non-SKS Prius, one that has fobs with a black logo on the back (not a silver logo). I successfully performed these steps on a 2005, by the way. The buttons work now to lock and unlock the doors and, when inserted into the dashboard, the new fob will allow me to start and drive the car. First, let's get the vocabulary straight. When I'm talking about the traditional metal key, I'll call it the "metal key". When I'm talking about the black plastic thing with three buttons on it (lock, unlock, panic) in which the metal key is stored and which itself fits in a slot in the dashboard, I'll call it the "fob". Also, I'll refer to your existing, perfectly fine fob as your "old fob" and I'll refer to the fob you just bought/found/stole as your "new fob". Note that these keys/fobs serve up to four different functions. Each is explained in detail below. * Unlocking the doors with the old-school metal key * Starting the computer so you can drive the car by sticking the fob into the dashboard slot -- The most important function! * Traditional remote door locking/unlocking with the buttons on the fob * SKS: The magical feature where the door unlocks when you approach it and car starts without you even touching the fob, which again, I know nothing about because my car does not have this feature. You'll know if you have an SKS key if the Toyota logo on the back is silver. Mine is black. The Metal Key This part is easy. Buy a blank OEM key from someone on eBay. I bought mine for $10, free shipping. This isn't very important. You don't really need this key on a regular basis. You'll only need it if the battery in the key fob dies or if the auxiliary battery in the car dies. If you can't find a genuine blank that fits into the fob, just have your hardware store copy your original onto a standard blank. It won't fit into the fob but hey, at least it'll unlock the door if your battery is dead. Addition: A fellow Priuschat contributor reported that his Toyota dealer quoted him about $8 for the metal key, including cutting it. Maybe my $10 eBay key plus whatever it costs to have it cut wasn't such a bright idea after all! I've locked my keys in my car on many occasions over the years. One solution to make that situation easier is to copy your metal key onto a $2.00 hardware store blank and tape a couple of super strong magnets to it and stick it to the inside of the wheel well above one of your rear wheels. I use magnets from old Sonicare toothbrush heads and have never had a key fall off, even after driving through deep snow and down bumpy dirt roads. Another good hiding place I've used with previous cars is under the hood near the windshield wipers but the Prius's hood is not magnetic, oddly. Anyone know why? The Fob (for operating the car) This isn't hard, as long as your new fob is not broken and you are able to follow simple directions. The whole process will take less than two minutes. 1. Insert old fob into slot and remove it 4 times in a row, then insert it a fifth time and leave it in. 2. Open and close driver door 6 times. 3. Remove old fob from slot. Car is in fob programming mode at this point. 4. Insert new fob and leave in the slot for a full minute. Watch the blinking red anti-theft light on the dashboard. When it stops flashing and goes dark, your new fob is all set. 5. Remove the new fob and you're done. You should test both fobs to be sure they work properly. The Fob (for remotely unlocking/locking the doors) This is similar to the previous directions except it has to be done at the full moon and you must not be wearing matching socks. 1. Open the driver door with no fob in slot and the doors unlocked. 2. Insert old fob into slot and remove it twice within 5 seconds. 3. Close and open driver door twice. 4. Insert and remove old fob once. 5. Close and open driver door twice again. 6. Insert old fob in slot and close door. 7. Without pressing the brake, press power button, wait a second, press it again, wait a second, press it a third time to turn car back off. 8. Remove old fob from slot. You'll be in "add mode" at this point. 9. Car should lock and unlock doors twice to verify it is in add mode. 10. Press and hold both buttons on new fob simultaneously for a second and a half. 11. Within 3 seconds, press just the lock button on new fob. 12. Car should respond with one quick lock/unlock to verify that the new fob is all set. If the car responds with two lock/unlocks, that means it didn't work. I don't know how to troubleshoot that problem. Maybe just try again. 13. To end this programming, open a door or put fob in the slot. The Fob (for SKS functions) Nice try. I warned you at the beginning of this document that I don't know anything about SKS since my car is not SKS-equipped. From the many, many threads and comments I've read on programming SKS fobs, it's clear that it is impossible to do yourself and must be done by your Toyota dealer. That said, one reliable source claims that following the directions above for programming the fob to remotely unlock your doors will also make the fob's SKS functions work, assuming it's a silver-logo fob. I'm curious to know if that really works so please post your results if you try it. That's it. I hope this helps! I wish I had found such a thorough document as this when I needed to program my own new fob! I bought my spare fob used on eBay for $60 shipped. I also bought a blank metal key for $10 shipped from a separate seller. Oh, and there is some discussion about new fobs (2006, 2007, 2008) being backwards compatible with older cars but older fobs being unable to work with those newer cars. I have no experience with this situation, though. One more thing. If you are unlucky enough to have lost all of your fobs and keep reading that you're totally screwed and will need to pay $1,200 for a new ECU, that may not be true. Check this out: http://priuschat.com/forums/care-ma...21501-end-don-t-lose-your-keys-else-myth.html Then again, if you're so unlucky to have lost all of your fobs, I'd bet that you won't have much luck on this front, either!