EGR Flow PO401

Hello, i have a 1998 Chevy Lumina that has a PO401 error code. Insufficient flow. My mechanic says egr passages are clear and the EGR valve is good.What else could it be?Does mine have the DPFE Sensor? Could that be the problem.The car has the 3.1 Liter V-6 with 137k. Just replaced the lower and upper intake gaskets, plugs,wires, and turn signal switch. This is the last problem im trying to correct. Thank-You!

Was the code there before the work was done?

Was the code there before the work was done?



It was on before the work

Ok, a bi directional scanner can activate the egr and determine whether it is working as the engine will stumble badly at idle. There is no sensor ithe pcm looks at map and airflow.

I've seen a few that had a big blob of oily "snot" laying in the EGR passage as a result of of an intake or head leak...it may look clear on the EGR end, but did he chase through it and actually see?

I've seen a few that had a big blob of oily "snot" laying in the EGR passage as a result of of an intake or head leak...it may look clear on the EGR end, but did he chase through it and actually see?

agree! he may have meant the egr tube is clear, but the tiny passage from the egr to the inside of the upper manifold is still blocked