1997 Ford Ranger EGR or DPFE fail?

[Bed]

Hi guys!

In the case below, do I have a bad DPFE sensor? It’s showing a constant 5V—is that a sign of failure?
Also, does anyone know where I can order an original Ford part online, preferably from a dealer near Washington, DC?

I got a 1997 Ford Ranger v6 4.0 from my dad, and it has a few issues that I want to learn how to fix.
I've been reading some manuals, and I need help diagnosing the P0401 and P0401-C error codes from FORScan.

hanks in advance

!

 

[Curious Hound]

Actually, the span of expected values is 0volts to 5volts and its showing a value of 4.57volts. Down below that there is a curve that suggests the egr valve is regulating flow. I’m not an expert at troubleshooting that system.

I had that low egr flow code on my 97 F150. I think cleaning or replacing the egr valve corrected it. Bit that was a couple years ago. I know I fought with it for a while and also tried to clean the egr tube and replaced the dpfe sensor. I’ll look and see if I documented it in a thread somewhere around here.

Follow-up; no. I didn’t make any further notes in that thread. I did run some Lucas fuel system cleaner for several tanks to try to help clean things up some more.

 

[Bed]

I read Tomco Tech Tips #33, which states that the DPFE should change the voltage.

I also tried items 1 and 2 above from another thread, but they failed (5v or 4,57v constant):

Tests: 1. Check the Differential Pressure Feedback EGR (DPFE) sensor voltage Key On Engine Off either on a scanner or by back probing the Brown/Light Green (BR/LG) wire at the DPFE sensor. The voltage should read roughly 0.4-1.1v depending on the sensor.

2. If the voltage is not correct (either above 1.1v or less than 0.4v), verify the Brown/White (BR/WH) wire is a good ground and that the Gray/Red (GY/RD) wire shows a good ground. Also make sure all pin connections are tight. If so, replace the DPFE sensor and retest.

3. If the voltage is correct Key On Engine Off, use a hand vacuum pump and apply 8" Hg vacuum to the "REF" port of the DPFE sensor. The voltage should increase to at least 4v. If it does not, replace the sensor and retest.


BUT the 3rd item may provide a clue that the EGR is locked open.

 

[Curious Hound]

BUT the 3rd item may provide a clue that the EGR is locked open.

Actually, that will provide a clue that the dpfe sensor is bad or good. Doesn't tell you anything for sure about the egr valve. The egr valve could be dirty and stuck or sticking because of gunk buildup and it wouldn't matter what the dpfe sensor does.

 

[Bed]

Actually, that will provide a clue that the dpfe sensor is bad or good. Doesn't tell you anything for sure about the egr valve. The egr valve could be dirty and stuck or sticking because of gunk buildup and it wouldn't matter what the dpfe sensor does.

You're right! The vacuum increases the voltage, not the EGR state. Thanks!
I'm learning! That's so cool!