What is the difference between planar and heated oxygen sensors?

Question

Why does this one use a heated one after the catalytic converter but planar before?

Answer 1

O2 sensors ONLY work when they are hot.  So after the cat converter the gases are too cool to correctly figure out the O2 level.

But many new cars use heated O2 sensor so that it can tell the O2 level even while the engine is still cold and warming up.

Good Luck....