If it says both banks are lean, then both sensors are reporting a lean condition, so if the other one was not damaged then they are both prolly working and are reporting an actual lean condition or have no power.
IIRC, if those codes are present the sensors may not have power. Smashing the wires could very well have shorted them out and popped the fuse. Look at the fuse (in the underhood box) and then check for +12 to the heater with the key on (use a DVM not a test light, these are computer circuits)
AFTER checking they have power, check for unmetered air getting into the intake (i.e. after the MAF), vacuum leaks, or a hole in the exhaust before the sensors. How does the truck run? Is it rough/hard to start?
look for any major leakage in these places:
The rubber gaskets on the intake pipe
The oil breather hose
Stuck PCV valve
Caps/ Hoses missing on vac tree
Rusted off EGR pipe
Holes/ rusted through bolts at the manifold to y pipe joints.
etc, etc