I have changed the intake gaskets were leaking , checked voltages to egr, tps, o2sensors, replaced egr tube was bad. Even shot the parts cannon at it. Egr valve replaced, 02sensor bank 2 sensor2 replaced and voltages tested. What am I over looking
These codes showed up after you replaced the manifold gaskets? Looking at P0405, the manual says to unplug the EGR valve,connect a test lamp between the EGR valve high circuit control and ground. Start the truck and command the EGR valve to 50%. The test light should lite up.
By the way, the EGR high control wire that you want to check with the test light is the red wire pin E on the EGR connector. I would ignore the O2 code for now.