1998 Ranger 3.0 P1401 CODE. I checke DPFE volts. Are any too high?

RonD said:

P1401 is a DPFE sensor fault.

DPFE has two hoses that run to the exhaust system, often to the EGR tube.
One is close to EGR valve and one farther away.
When engine has a load on it the computer will open the EGR valve to cool the cylinders which keeps NOx emissions down.
The DPFE sensor tells the computer the pressure difference at the EGR valve and at the exhaust manifold so computer can tell how much exhaust is flowing into the intake.
Computer pulses vacuum to the EGR valve to open it a little or all the way based on DPFE feedback.

When you burn gasoline(H) with air(O) one of the by-products is H2O(water), this is why exhaust systems rust from the inside out, and tail pipes drip water out.
This water vapor will be in the hoses going to the DPFE sensor, and over time this condensed moisture(when engine cools off) will ruin the DPFE sensor.
Which is why it is not uncommon to have to replace them every 60k-80k miles depending on driving conditions.

DPFE sensor should show .5v to .9volt at idle, EGR valve is closed so no pressure difference, yours is high so that is probably the source of the code.
Could be EGR valve has some carbon build up so is not closing all the way, but you should notice a rough idle if that were the case.

Retest DPFE with key on and engine off so there can be no pressure difference, should be low, .5-.9v

Always clean out and check the DPFE hoses for water and cracks as well

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RonD said:

DPFE is an emission device, like a Cat converter or EVAP system.
These rarely effect performance when there is a problem.

Loose gas cap can set EVAP code but you wouldn't have an running problems
Cat might not be cleaning exhaust as well now but unless it was blocking the exhaust engine would run fine.
DPFE out of range just means computer might not use EGR valve or would use it sparingly, so wouldn't effect performance.

These things don't help or hurt performance, they are used so you and your kids and grand kids might have some breathable air left

"They don't make them like they used to"..............well DPFE sensors haven't been around all that long and they do tend to fail, most avoid Ford DPFE sensors, metal or plastic, they say 3rd party tend to hold up longer, but can't say myself

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