OK, now I'm pulling my hair out!! I have a 1998 Chevy PU and I have been getting code 0401 for over a year. About 3 months ago, I replaced my EGR intake, with a NON-EGR intake. In the last 3 months, I have replaced the vacuum pump, all 3 solenoids (wastegate-green dot, and both egr solenoids- white, and red dots), and the boro/map sensor (on the firewall). Plus, I have replaced lines checked, & double checked for leaks with a vacuum gauge. After the intake switch out, I not only got 0401, but now I get 0400 also.
I had a mechanic recommend changing out the eprom on the computer, but my 1998 does not have the eprom. Can anyone PLEASE help me??? I dows run great. And withe the non-egr intake, absolutely NO smoke during heavy acceleration. Thanks!!