Hi! First off before you go work on the sensor, I would check the gas cap
You're going to want to make sure that there is a tight seal on the gas cap, and that when you close the gas cap, it clicks or locks (depends on the car.) Best way to clean the gas cap is to spray some WD40 (NOT INTO THE TANK) around the gas cap on the car. Worst case you do this and the error code doesn't go away, I would buy a new gas cap
Now let's say that the gas cap is all good and it didn't solve the issue. Then you need to replace the Fuel pressure Sensor. [link|https://www.youtube.com/watch?v=CcrcGZoaEzI|This video shows you how to|new_window=true]
Now I can say that for your car being a 97-01 Toyota, aftermarkets are about a few hundred dollars compared to paying 300 through Toyota. I would replace the sensor because if you don't, your car will have trouble starting up. Happened to my honda