3rd plug, aftermarket stereo

I just installed a new pioneer 6400bt and everything except the ac works fine. The stock stereo had 3 plugs and the wire adapter only uses two. What is the third plug used for? It has 3 wires that feed into it, white/red, purple and yellow/black. Everything on the new unit works but was just curious
Darren

 

Bump.....Curious about this also.

 

Steering wheel controls if im not mistaken.

 

Mine didnt have the steering controls but whatever, it is it doesnt appear that important. Nobody responded with "that was the anti implosion switch" so i guess we are good.

 

Right my truck doesnt have the steering wheel contols either but it has that plug which i read somewhere was for the controls. I believe most prerunners are prewired for it.

 

Im guessing the lighting for the switches?(for the oem panel)

 

that plug is for the w=steering wheel controls all tacos are prewired for them. As far as the AC goes you should not have needed to remove the controls to do the radio but something could have come unplugged. If not check your fuses.