I'm not an expert in this, but I think it won't work.

I think I saw something about turning on aux input (if you have one) on Pioneer unit without emulator, but I'm not sure. But definitely you cannot do that in CD-changer mode, because your unit knows nothing about CD-changer without emulator or real CD-changer and leaves audio input disabled. IMHO.

Вот тут, вроде, человек заборол таким образом - с ипользованием внутреннего компаратора меги на прием и портов напрямую на передачу: http://www.sigmaobjects.com/toyota/