can replacing the o2 senser help fix code po401 and code po420

Question

I have replaced the egr valve and it did not help.

Answer 1

Hi there,

Changing the O2 sensors could possibly do something with the P0420 code, but it will do nothing for the egr code. You should check for blockages on the egr port and make sure the egr solenoid is sending vacuum to the egr valve.