meaning of code p0420 for alero

Question

chech engine soon lite is on. the code p0420 comes up on diagnostic. I need information as to what this means as to sensors and the catalytic converter.

Answer 1

This means the converter is not operating properly. 99% of the time this is a faulty converter that causes the issue. In some cases it's the rear O2 sensor. A scan tool is needed to read the wave pattern of the rear sensor to try and determine if it's the cause.