Can anybody help with this problem. 97 F-150 4.6L has check engine light on, code PO401. Insufficient flow of EGR. I have cleaned valve,tube and checked manifold all ok. Also have replaced solenoid & backpressure valve. Still lit and same code. Also ABS light on all the time,had code 9 , replaced axle sensor test ok,code16 but light is still on.Any thoughts would be helpful.

 

I had the same code on my 99 Ranger 6cyl. After surfing thru the forums, I found that the DPFE sensor, (that is what it is called on the Ranger) was the culprit. I replaced it (59.00 PepBoys) and it solved my PO401 code plus some other problems with performance. Hope this helps. Thanks to all the other posts regarding this code!

 

Removed for test forum and sent to 97-2003 forum.

 

Removed from test forum and sent to 97-2003 forum.

 

I fought the P0401 code for weeks including changing the EGR valve, sensor, and several 6 packs. The new EGR valve cleared the code only to have it return a few days later.
My problem turned out to be the EGR port holes in the manifold. Carbon build up in the port was restricting flow.
With the EGR valve off use a rigid tool (metal coat hanger works) to break up the carbon and use aerosol carb cleaner to ensure that the port path is clear.
It solved my P0401 hope it works for yours.