sorry i posted wrong code its not 402 , its po401

What parts did you replace? Do you have a digital multi meter to do some testing? Have you checked all the vacuum lines and such within the EGR system to make sure none are cracked or burnt? Here is a pic of the components in the egr system.

no meter , installing a tps today, installed egr solenoid , delta pressure sensor , and an iac . still no improvements .looked at vacuum lines and do not see any cracks .

Ok what you need to do now is use the pic included and check the vacuum lines and make sure they are not cracked or pinched. if all is good then you need to start the truck and make sure the vacuum supply is getting vacuum. Do you have a scan tool that can live stream data? What engine do you have?

thanks for your help, no scan tool. i checked all lines all were good except one on top of throttle body that goes to a solenoid on the firewall. i also read where if you unplug one injector at a time you can trace a coil problem. also its a 4.6 . and thank you again for your help

As for coil problem yea that will work as long as the injector is not the problem. If you had a missing cylinder issure it would have a P030? code. So replace or fix that vacuum line and check for any vacuum leaks around the EGR. Thanks and you are welcome.