1998 Toyota Sienna Car Stereo Wiring Diagram Whether your an expert Toyota Sienna mobile electronics installer, Toyota Sienna fanatic, or a novice Toyota Sienna enthusiast with a 1998 Toyota Sienna, a car stereo wiring diagram can save yourself a lot of time. Automotive wiring in a 1998 Toyota Sienna vehicles are becoming increasing more difficult to identify due to the installation of more advanced factory oem electronics. 1998 Toyota Sienna OE Wiring Harnesses & Stereo Adapters Toyota Sienna 1998, Aftermarket Radio Wiring Harness by Metra®, with OEM Plug. For aftermarket stereo. Metra preassembled wiring harnesses can make your car stereo installation seamless, or at least a lot simpler.