Im planning on getting a prius c in the future. so m keeping an eye for the Head unit replacement threads, but one thing i wondering if its possible to modify the usb/aux input on the dash to work with an aftermarket unit. any ideas?
Not sure. Personally I don't like the location of the factory connection so I'm glad to no longer use it. It appeared to me that the USB connection went into the back of the factory stereo on one connector, so the aux in must be somewhere else.. Which could be more easy to hook into if you knew the wires. USB.. unless you could get an adapter to fit whatever is on the Toyota one (it's odd) you could be out of luck. Then of course you'd need a head unit with USB & Aux Inputs on the back, do they exist? Otherwise you'd have to run wires to the front of the head unit which would look pretty lame.
I haven't looked at the back of the head unit on these cars yet, but Toyota's over the past few years use a customized USB connector on the back of the radio for connection. I had a 2011 head unit from a Scion in my Yaris which had such a connector, but I was unable to find a company that made the mating plug. (I used to work for a small electronics/wiring harness company, I had all the resources you could imagine for connectors and I couldn't find one) I ended up taking the radio apart, sacrificing a standard USB cable and soldering the wires directly to the main board of the radio. I wouldn't recommend that route unless you seriously know what you're doing. Since these cars already have the USB cable, it might be easier to cut/splice a new connection. I also dislike the location of the plug. My iPod will stay in the car at all times and phone will connect via Bluetooth. So, my plan is to order a USB extension cable, then pull the connector out of the dashboard and tuck it in behind the glovebox or something. The connector looks to be a standard Toyota switch socket, so getting a block-off isn't going to be hard.
Exactly what SquallLHeart said. Comepletely Doable. But a pain. We do them frequently with aftermarket head units. Your aftermarket head unit choice will also influence what modification you wi have to do. Some of the rear USBs aren't that long. Also some head units have proprietary cables that have to be used. Given the problem that a lot of people are having with Entune, that was a major influence into my decision for ordering a 2 and not a 3. Aftermarket head units will always get you more bang for your buck.