Which 1st: DPFE of EGR?

[Evicerate]

I recently got the wonderful check engine light on my 94 XLT to come on. I pulled the codes from it and got the following:
KOEO
335 PFE or DPFE sensor out of self-test volt range
522 Not in park or neutral during test (not really important )

CM
332 EGR valve not opening not detected

So, after reading all of the posts on the subject I could find, my question was should I try and clean the EGR valve first, and if so how would I do that, or do I go and replace the DPFE first and hope that was the original problem?

Any help would be appreciated.
Thanks

 

[MrShorty]

A KOEO code, because it is set with the engine off, almost has to be an electrical fault. When the engine isn't running, the cleanliness of the EGR valve isn't going to effect the PFE/DPFE's output. (For that matter, I'm not sure the EGR valve can even open or close because there's no engine vacuum to operate the valve, isn't that right?)
That said, I'd focus on the DPFE circuit. A lot of people like to start by replacing the DPFE. I would at least inspect the wiring between the DPFE and the PCM before replacing the sensor.

 

[Evicerate]

Thank you.
I figured the DPFE would be the place to start, but I wanted to make sure before I took stuff apart or threw any money at the problem. I'll let you know how it goes.
Thanks again.

 

[pmcmaster]

If an EGR error is thrown there are several causes, MAF sensor also Throttle position sensor (TPS), Engine coolant sensor (ECT) and Trasmission Control Control i.e. the control that controls the controls (only Ford could come up with that one!!!) (TCC). EGR tests Disconnect harness to EGR vacuum regulator, with ignition on there should be voltage at the harness end. With ohmmeter check resistance of regulator - for DPFE systems should be 26-40ohms (PFE systems should be 20-70ohms). Voltage at the harness end of the DPFE terminal VREF should be 4-6 volts (ignition on engine not running). DPFE test, at the DPFE connector identify the SIG and GND wires that run to the PCM. backprobe these wires with voltmeter, with engine running COLD (No EGR) there should be 0.75 - 1.25 volts (black plastic DPFE) or 0.35 - 0.8 volts (aluminium DPFE). As engine warms and EGR is called the voltage should increase to 4.0 - 6.0 volts. If tests values are incorrect - check the vacuum source to the DPFE if ok the DPFE is probably faulty. As per Haynes - hope this helps

 

[97BlackX5.0]

youf dpfe is propably clogged and not working.... buy one try it and see if the code goes away.... if not then put the old one back on and return it ...

 

[Glacier991]

The DPFE is a weak point. I'd venture more EGR valves have been unnecessarily replaced because of bad DPFE's. I'd suspect it first. WAY first. Candidly the poor thing is subjected to intense heat and has a cooler side and that leads to clogging and other failures. The hoses fail frequently as well (largely heat related failures in my opinion). It's a problem child in the EGR system and the leading candidate for replacement.

 

[Evicerate]

Well, I finally went and got a replacement DPFE. Reset the computer after I installed the new one, and BAM, no more CE light. It's not even been a week, but I've driven over 300 miles on the new DPFE and have yet to see a CE light.

I appreciate all of the input and hope that this will help someone else in the future and save them from buying an unnecessary EGR valve.