Puzzled by the inoperable navigation system, i decided to do some research. A little history first. On very rare occasions, the JBL head unit would not come on at all. We experienced this problem less than five times in the 2 years we've owned this van. The unit would not come on for a few minutes after starting the vehicle, but would eventually become operable (usually after 5 minutes). Two weeks ago, the unit would not come on at all. Every button was unresponsive. The rear entertainment system worked fine, however no audio was heard thru the speakers due to the head unit being off. After looking at several RAD (radio) fuses in the engine compartment and driver's side fuse panel, as well as removing the head unit and ensuring proper connections, the JBL navigation unit suddenly began working again. It word for less than 1 day before returning to the dreaded "black screen". I found a list of all radio fuses from Sienna.org and inspected all of them. They all appeared to be in good condition. After re-installing the fuses, the radio again began to work.
My understanding at this point is that there is some poor connections in the fuse box that is prohibiting the correct amount of current to be supplied to the JBL head unit. This could be due to rust or not properly seating the fuses. Either way, the problem appears to be solved. BTW, the JBL head unit costs $3,700 from the Toyota dealer. Glad this didn't require a replacement!
Now, if I could just figure out how to fix the heated driver seat problem without taking the seat apart or going to the Toyota dealer for service.
