1996 Ford Ranger 4L V6

Issue:

• Corrected issue with poor idling and error codes related to EGR system - replaced EGR valve (missing) and EGR tube (holes).
• 2 days after repair CEL came on and is reporting error code of P0401 (EGR flow insufficient) and P0136 (02 sensor circuit malfunction - Bank 1 Sensor 2).
• Did not replace vacuum lines or DPFE

Looking for suggestions or help on what to check first and how to fix - ie don't use aftermarket DPFE. Any input would be appreciated.

Good news replacing EGR valve and tube fixed idling issues.

 

Welcome to FTE.
Looks like you've been busy on this one.

The O2 code is for it's heater, maybe wiring, maybe corrosion in it's electrical connector, maybe the sensors heating element is bad.
If so, the sensor will be slow to heat up & come online to do it's thing.

As a side thought, most folks think about replacing both of the upstream O2 sensors around 100K miles, as their swiching speed/sensitivity gets lazy/slow & mpg gets bad, ect.
So it's recommended to replace them in pairs & with an OEM like design.

There are two current on going P0401 threads & here is a suggested trouble shooting test scenario I posted that you might consider in your trouble shoot.
https://www.ford-trucks.com/forums/9...ml#post9209031

Your right, the DPFE sensor has earned a place at or near the top of the suspect list, so you might begin testing there.

Then if no joy maybe check the lines to the EGR valve, to make sure they & it's feedback orifice aren't clogged with carbon, then the EVR, in about that order.

Let us know how the trouble shoot goes.

Edit: Seeing as how you seem to like turning your own wrenches, be sure to check out the "Tech Info" thread atop this forums thread listing page, all kinds of helpful info links there.