I've sprayed B12 and try to clean out the EGR valve and the solenoid (not sure what it's called) above the EGR. The diaphragm works. Did I not clean them enough?
Doug

 

Usually, if the EGR is working ok, the DPFE sensor has gone bad giving a false reading.

 

They probably weren't dirty.

It's usually either a faulty DPFE sensor or the EGR ports behind the throttle body are clogged that causes the P0401.

Apply a vacuum to the EGR valve while idling.

If the engine stumbles and stalls, the ports are clear and the EGR valve is operating. Go after the DPFE (98% liklihood).

If no change, either the ports are clogged (98% again) or the EGR valve has failed.

Steve

 

Thanks for the help. I think I'm going to find instructions on how to clean the ports on the plenum. thanks for the help.

 

DPFE is located on drivers side against the firewall.....see couple tubes comming into the top of it.....it's like 3 inches tall by 1 inch square or somethign close to that.....mine went bad....try like project sho89 said about the egr first to see if thats working though for sure.....i got my DPFE sensor from a friend thats a mechanic for 15 bucks......thats your cheapest bet for the part if you have the hook-up