I normaly only work on domestic autos however this is simple. Check your owners manule for the locations of all fuse banks. Next look for any fuse related to your horn. Check each one for a bowen fuse(burnt center seperated metal strip). Replace with like fuse I.E. 20 with 20. Note do not replace with greater or lesser fuse, you will damage your electrical system. If all is well an no horn then compleatly disconect the batery for three minuts an reconect snug. If still no horn run a code reader to see if the car tosses a horn code. If no horn, fuse problem, and or code take it to a Toyota delership, this should be fixed for free or up to no more than $199.00. I know you should go directly to a code reader however not all of us are rich enuf to buy one or to go right to the dealer. This is the best way to go about any auto problem before flushing away your bank acount. I hope this helps.