Toyota 86 Headunit into ZRE152R Corolla?

[DAL32]

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.

[ChrisZRE]

I have done this conversion and you need all three plugs as the last one is the sound.
Take it to the dealer, I took mine to Castle Hill Toyota, and they have 2 harnesses, each @ $10.

[DAL32]

Cheers, thanks for that. Did you keep steering wheel control function?

[ChrisZRE]

Nah didn't have steering wheel control. Mines the pez Ascent model haha

[DAL32]

For anyone needing a reference, the aerial harness is the only one available (a simple conversion) and the part number for the Corolla to the new gen head units (I can't imagine that an 86 GT unit would be any different to the new shapes of Corollas head units which look the same) is PZQ60-00141