Engine Light

P0432 Main Catalyst Efficiency Below Threshold (Bank 2)

Diagnostic fault codes never say to replace parts or that one is bad. This is a perfect example. The code means the catalytic converter is not doing its job, and you need two properly-working oxygen sensors to determine that. The sensors you replaced were doing exactly what they were supposed to do. That is to report the amount of unburned oxygen in the exhaust.

Typically your mechanic will induce a forced rich condition, then a forced lean condition, and watch the sensor data on a scanner to see how the oxygen sensors respond. Once they're verified as working properly, the solution will be to replace the catalytic converter.