P0161 code, have power

[Bryyrtw1981]

I'm throwing a p0161 code along wit other ones but I tested all 4 at the pink wire and they all have 12 volts. I do need a new timing chain and gears but wasn't sure if that would make it throw the o2s heater code.
Also my rear brakes lock up pretty easy. Would this b the proportioning valve,abs module, or the master cyl. Any suggestions ???