My brother just bought a 2007 Corolla, pretty sure it's ZRE152R even though the dealership wrote down ZZE122R. The first thing we tried to do is swap the headunits out because his only has Aux input and no bluetooth whatsoever. I was thinking it would be a straight swap, which it sort of does look like from the main plugs, but there is a third plug which is different. Unsure exactly what it does, but the first two look a lot like power and speakers, so perhaps this third one does steering wheel controls or something? The 86 doesn't have steering controls and yet I have literally no idea what the 86 stereo harness looks like because I got that one done by a car audio place. Felt this would be an easier/cheaper option than going aftermarket, as the unit has BT Audio and phone, as well as voice control. So my main question is, whether the stereo will work with the two main plugs, and what is the function of the third plug? If it is essential, is there any sort of conversion harness? I was under the impression that people do upgrades of old Toyota head units to these new ones all the time, but my googling hasn't revealed a lot.