2002 Explorer Sport Trac: P0171, P0174, P1401, P1451 at the same time | Ford Explorer Forums - Serious Explorations

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2002 Explorer Sport Trac: P0171, P0174, P1401, P1451 at the same time


New Member
April 10, 2019
Reaction score
City, State
Greater Detroit, MI
Year, Model & Trim Level
2002 Sport Trac
Hi there! My 4.0L SOHC engine has been running quite poor in the morning lately. While I realize that when it's very cold outside the engine will take longer to start, I did not expect it to be extraordinarily loud (consistently greater than 95 dB on my phone's microphone) and very rough (stuttering and bucking, but not stalling).

I ran a DTC scan with my copy of FORscan and found the following codes appearing, which may or may not be related:
  • P0171 and P0174: System too lean (banks 1 and 2)
  • P1401: DPFE sensor circuit high voltage detected
  • P1451: EVAP control system vent control valve circuit malfunction
From what I understand, these codes are seemingly related; I haven't received the warm embrace of a check engine light just yet, despite the fact that these codes are supposed to trip a check engine light. I also noticed in my research that the DPFE Sensor has a Technical Bulletin out (see https://www.autocodes.com/uploads/ford/04-11-1.pdf) and could potentially cause both the lean codes and the EVAP code.

Has anybody else seen these codes before? Is it repairable without a dealer?

Sounds good. I'll take a look at that and see what happens. Could the DPFE sensor also have something to do with it too? Or is that just a symptom of the PCV elbow leaking?