P0405 GMC -

Question

What do we do to fix this? We have replaced all o2 sensors and the EGR valve?

Answer 1

HI there,

The map sensor might cause this code if it doesn't see a change when the egr is suppose to open. Also, check and make sure you don't have any blockage from the egr. If there is a blockage, even if the egr is working, then it will give the code.