DPFE or EGR?

jeremyjudd · Sep 6, 2008

Hello all! This is my first post. I have a '94 Ranger with the 4.0 ltr engine and she's got a check engine light on. I hooked up my handy dandy voltmeter and she's popping a 332 and a 337 error code. Apparently the 332 means her EGR valve isn't opening right, but the 337 means the voltage is too high on my DPFE. How do I figure out which part is malfunctioning here? I tested the electrical connect for the DPFE and it's dead-on perfect, but I don't know how to test the DPFE itself. I removed the EGR valve and it seems to close and open when I'm sucking on it.

Neither of these parts are cheap. Any suggestions? It's running really warm (about the halfway mark on the heat gauge, when running right it never gets more than a quarter of the way up) and I know that a malfunction in the EGR system can cause this.

Help me out? Thanks!

Yellowsplash · Sep 6, 2008

I would replace the DPFE first before replacing the EGR valve since you have a code for it. I would just clean the carbon off the egr with some carb cleaner and bolt it back on and see what that does for ya.

jeremyjudd · Sep 6, 2008

Sounds like as good advice as any. And I think the DPFE is about 10 bucks cheaper.

I'll give that a shot and see where I stand.

Explorin94 · Sep 6, 2008

Check too see if the hoses going to the DPFE sensor are spongy. If they are replace them first with something equivilent to what they are first.

Donnie strickland · Sep 6, 2008

OK, what kinds of codes are these? KOER, KOEO or continuous memory? If KOER, the shop manual says:

Diagnostic Trouble Code (DTC) 332 indicates the Pressure Feedback EGR (PFE) / Differential Pressure Feedback EGR (DPFE) sensor signal to the Powertrain Control Module (PCM) did not change when the PCM output a duty cycle to the EGR Vacuum Regulator (EVR) solenoid requesting EGR flow. Possible causes are:

Icing
Obstructed EGR passages
Vacuum hose leaks.
Obstructed vacuum hoses.
Damaged EVR solenoid.
Damaged PFE/DPFE sensor.
Damaged EGR valve.
Damaged PCM.

Diagnostic Trouble Code (DTC) 336 or 337 indicates that Differential Pressure Feedback EGR (DPFE) circuit voltage is higher than expected at zero duty cycle.
Possible causes are:

Damaged EGR Vacuum Regulator (EVR) solenoid.
Damaged DPFE sensor.
Damaged or contaminated EGR valve.
Vacuum hose routing.
Damaged Powertrain Control Module (PCM) .

Don't buy anything yet, except maybe some vacuum hose. Check these first, as Brett Simpson says, and replace any hose that's at all suspect.

Once that's done, if you still have a trouble code, I would suspect the EGR valve, or possibly the EVR solenoid. If your engine is indeed running warmer than normal, you have provided a clue.

Jason_12_02 · Sep 6, 2008

working in the parts business, i see this all the time. 80% of the time its the DPFE. On my ranger i replaced the DPFE and the solenoid and that fixed my light problem and gave me about 2 more mpg (not kidding!). The parts were cheap for me so i just replaced both atthe same time.

jeremyjudd · Sep 9, 2008

Replaced the DPFE. No dice. Checked all hoses. No leaks/obstructions. Replaced the two going to the DPFE. No dice. Still a check engine light, these are key on engine off tests. Thinking EGR valve? Also heard an engine temp sensor will throw the light and read the same as EGR/DPFE code. Engine is still running warmer than normal. Whad'all think? Also removed EGR, cleaned and put back on...

MAKG · Sep 9, 2008

No, a KOEO code on the DPFE indicates an electrical problem with the DPFE circuit. Check all the wiring in that circuit (as this is the most likely fault), then verify power and ground to the PCM and to the DPFE, and if it all checks out, replace the PCM. Be thorough; most condemned PCMs are actually good.

"Higher than expected" (out of range) voltages are usually a sign of bad grounding for the sensor.

jeremyjudd · Sep 11, 2008

Evr?

I've heard the EGR vaccuum regulator can also cause this problem. Checked wiring. Everything checks out with the specs in my manual. Seems like if the PCM had gone south it would be running a lot worse. No noticeable signs of a problem except the light is on and it's running warmer than usual.

Thoughts?

Earl43P · Sep 11, 2008

Go here http://www.tomco-inc.com/techinfo.aspx and read up on Ford EGR.

Pretty sure you can ohm out the egr solenoid and there's a vaccuum test to see if it is opening/closing.

http://www.tomco-inc.com/Tech_Tips/ttt32.pdf page 2

fordwheelinman · Sep 11, 2008

You need to check to see if the passages are blocked. Start the engine and let it idle, then use a hand vacuum pump, or your mouth, to pill a vacuum on the egr valve. If the engine stumbles and acts like it wants to stall, or stalls, you know the egr and passages are functioning properly. If the engine does not stumble or stall, than you have blocked ports.

NOW, if the ports are blocked or the egr valve itself is not allowing sufficient flow, it could be throwing off the voltage reading from the DPFE sensor to the computer, thus giving you the voltage code. Check the DPFE sensor to see what it is made out of. If it is made from a metal like material, i suggest replacing it with a part from your ford dealer. The old style metal part is widely know for causing issues, had to reaplce at least a dozen in two years on vehicels. Just because the egr valve is working when you take it off, doesnt mean passages arent blocked.

Donnie strickland · Sep 12, 2008

If KOEO, then these codes would most likely indicate an electrical problem, just as MAKG says above. Shop manual says check for loose/broken wiring, and check all connection sockets for loose/broken pins. Check also for poor grounds.

It also says the EVR solenoid could be the culprit, or a damaged PCM (which is extremely unlikely).

And of course it could just be a bad EGR valve. But I'd check the cheapest things first.

fordwheelinman · Sep 13, 2008

what shop manual?

1987ranger · Sep 13, 2008

pull a vacuum on the egr, the engine should run rough or die. if it does not the egr valve is no good

Donnie strickland · Sep 13, 2008

fordwheelinman said:
what shop manual?

Ford.

DPFE or EGR?

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