failed smog test due to code po 401, had all parts repalaced to fix problem. passed all smog parts of smog test but failed over all test due to po 401 triping CHECK ENGINE LIGHT.
failed smog test, check engine light. on 1997 Ford E-150
This problem can be due to carbon build-up in the EGR system. It's important that a diagnosis is performed to determine the fault, merely replacing parts in the hope that it will fix a problem is a waste of money, as you are finding out. Check out this article about this fault, and pass it on the the mechanic if they are having problems diagnosing this: http://repairpal.com/OBD-Code-P0401