Insufficient EGR: four cylinder. Replaced EGR Modulator and valve, Replaced some cracked vacuum hoses to the EGR components, and still can not clear the P0401 code. What should I check next? Looking at MAP/MAF sensor but everything I hear about this, says they rarely ever go bad…could this be it? Would this be the next component I need to replace? What else could cause this code to trigger? Failed emissions inspection twice now.
Thanks for all the help in advance!
Glenn
When my 94 Toyota Previa threw the same code the dealer replaced the EGR modulator and valve (at considerable cost) before cleaning out the metal pipes in the EGR system with pipe cleaners. It turned out to be a build up of carbon in the pipes between the vacuum hoses. Once they cleaned that out the light went off and I never had an EGR problem again.
I’ll give that a try…kicking myself now that I didn’t think to do that while I had it off when I replaced the valve…here I go again.
Thanks for the advise!
Glenn
Don’t forget to clear the rest of the path through which the exhaust gas is diverted as well. The orifice in the throttle body can get clogged with soot too.
Will do…thanks!
It can also clog up in the passage in the exhaust manifold as well. It needs a clear path all the way from the exhaust manifold to the intake.