Since almost everyone has to deal with the TPMS light on the dash coming on, here is the likely situation on a 2006 Rav 4.. One of the valve sensors inside one of the tires has failed. It takes a special tire scanner to tell which tire sensor is bad so a garage is usually needed. However, you can get a good replacement sensor in advance online for your specific vehicle for $30. When you go to the garage, expect about $30 to install the new sensor in the tire they diagnose as bad, $15 to rebalance the tire, and $25 to digitally relearn the sensor to the computer. All you can do to save on this repair is to get the part yourself. No way to DIY. Or you can just ignore the light and save $100.