Pesky P0401 Code Keeps Coming Back

[rgpinder]

Insufficient EGR flow. I've been trying to clear this code for a week now. Here's what I've done so far. 1) Replaced the EGR Valve 2) Replaced the DPFE sensor with one of the newer plastic units 3) removed the entire throttle body and cleaned it. Then cleaned out the passage between the intake and the EGR valve. There was some carbon build up in there.

However, after all that, the code keeps coming back. What should I do next?

 

[Rearanger]

My Ranger does not have an EGR but looking through my FSM this is a complex system to troubleshoot.

Couple of things you might be able to do is inspect the hoses going to the DPF sensor. There is a small tube and large tube that connect to the exhaust through the orifice tube. I'd pull them and make sure they're clear and have no leaks, as well as check that they are clear at the orifice tube. These hoses communicate the upstream and downstream pressure across the orifice (Differential).

The orifice tube also may be blocked at the orifice. I'd pull it and clean it.

 

[JP02XLT]

The hoses are well know to get carbon filled especially at any bends, ReaRanger is dead on any blockage or restriction in them will cause similar problems.

JP02XLT

 

[rgpinder]

Just wanted to close the loop on this problem. The fix was to swap the REF and HI hoses at the DPFE. Somehow I got them backwards when replacing the DPFE unit. Gone a week with no CEL. Yippee!