Error code PO401 EGR flow insufficient

2000 Ford Ranger XLT 3.0
Prior to taking my truck down for the annual NY State inspection I hooked up my handheld scanner get an idea what, if any problems might pop up.
Even though my check engine light is not on I still get the PO401(EGR flow insufficient) error code.
My first question is: Would a medium leak in the muffler cause enough loss of back pressure to set this code off?
Second question: Even though my scanner is showing this error is it possible to still pass an emmissions test? Remember the CEL is not lit, now anyhow.
Some background on the truck. I use it in the woods 95% percent of the time but because of those short and rare trips over the highway I still need it registered and insured and unfortunately, inspected. So I don't care if the muffler is making noise and if it isn't the cause of the code I don't want to fix it. By eliminating the muffler I can go ahead and start loooking at the SGR valve and tube, DPFE sensor etc.
Thanks all

 

I don't think the muffler would be a factor. More likely I think would be carbon buildup in the egr itself or a bad vacuum line into or out of the egr control. Vacuum lines are usually very easy to check and cheap to replace (provided you use generic vacuum hose and not OEM Ford parts).

 

Thanks for the speedy reply. I tend to think like you that the muffler, no matter how bad, isn't a factor. The cat converter probably creates enough back pressure for the EGR. I guess I'll have a go at the EGR,DPFE, tubes and vac lines tomorrow. If I had to guess I'd say that carbon build-up is first suspect with the DPFE sensor next in line.

 

DPFE ...if original, is a Known Problem. There is a redesigned unit to eliminate the false trips.

There is a vacuum solenoid that controls EGR function...Follow the GREEN TUBE from EGR to solenoid. Disconnect the vac connector from the solenoid and ensure (With the engine running of course) that the RED tube has vacuum. Replace the connector and remove the plastic "CAP" from the top of the solenoid. With your "PINKY FINGER" Block off the small "Nipple" under the cap. The engine should sputter and stall as the EGR valve Opens.

The muffler leak, Could Conceivably force a 401 code, but not likely. However, The Exhaust leak may be an Issue with Inspection Criteria.
If the light is not on, The emissions analyzer will look for the "TRIP-COUNT" in your PCM. Provided the Trip counter has sufficient "PASS" cycles....The code will not be an Issue with Your Inspection.

 

I think I did that but in a different manner-I disconnected the vac line from the EGR, attached a clean hose to EGR and sucked on it. EGR valve seemed to function okay Truck sputtered some but didn't die. Without motor running I can hear/feel the EGR valve go up and down. Soosn as I find some decent back probes I will test the current to the DPFE

 

well, why don't you simply remove EGR valve and clean it with a good spray cleaner? it's usually a 10 minute job. then either reset your codes or leave negative battery cabel off for night and see if code comes back.
i developed a habit of routinely cleaning EGRs at over 100K miles. quick and easy maintenance.

 

DPFE's are notoriously failure prone on ford products...clearing the trip counter by disconnecting the battery cable will cause you to fail the emissions test as the analyzer looks for that...keeps people from disconnecting the battery and then driving into the inspection lane.

I'm curious...how can your vehicle pass ANY inspection with a bad muffler?

 

I guess it's because I'm kind of a anal type person. I prefer to do things in order with the simplest and least expensive things first. To wit:
1. Inspect all visible hoses
2. Hook vacuum pump (or mouth) and test if the EGR valve is at least going up and down
3. Check DPFE voltage with key-on, engine off
4. Check DPFE voltage with engine running at idle
So now I know that the DPFE is working properly ( a common issue with Fords) and the EGR valve appears to be working.
At this point I have eliminated several possible causes and I haven't got my hands dirty or spent any money.
Now I will grab a wrench and remove EGR and begin picking out the carbon build-up which at this point I'm 90% certain is where the my problem lies.

 

I have a handheld that tells me when vehicle computer is ready again to test after re-setting codes.
As to the muffler, you got me there. Damned if I know. However, I got through last years test with the same leaky exhaust. And I just got through reading inspection requirements for NY State and found nothing at all about mufflers. This is an edit. I found the link to NYS Inspection
http://www.nydmv.state.ny.us/broch/c-50.htm
Like everything else the government gets into it gets insane. They will nit-pick over a 1% increase in emmisions but it is okay for me to kill my kids, wife, and dog with carbon monoxide.
While we are off topic I will add this. Every so often the cops and local governments around here go on a real binge of issuing tickets for seat belt violations. We also, in New York have a law against cell phone usage while driving. I know, nor have I ever heard of, anybody who was ever ticketed for the cell phone violation. It's just not enforced.
So, here they are enforcing the hell out a law that can only hurt the person who is not wearing the belt and nobody else. while ignoring cell phone violations that endanger everyone else on the road. Ride a motorcycle for a while and you will get a real clear picture of the danger to others.
So I guess the muffler is just another example of crazy laws and non-laws.

 

Problem there is you should have no EGR flow at IDLE. The problem arises at Driving speed, when the PCM commands the EGR to open, but DPFE doesnt see a Change. Testin at KOEO, and KOER, should produce the same, If not very Close test results, but dont verify "OPERATING" conditions. Your EGR solenoid is "Modulated" to provide almost infinite variations to egr "LIFT POSITION" . Only your PCM knows what resistance value to expect for a specific amount of "LIFT".

Also.... From DPFE to Exhaust Manifold...You will see 2 Grey or Green SILICONE hoses. CAREFULLY check them for ANY DAMAGE. Trucks especially , because of their location, can suffer Burn damage very easily as a result of EGR system failure.

 

I'm aware of that. However, the voltage checks show that the DPFE is at least working and probably could see the difference if one existed. The problem lies in that there is, in all llikelihood, a blockage so that the DPFE can't register it.

Step 1) Check the condition of the vacuum hoses going to the DPFE sensor and the EVR. Look for cracks or tears. Replace the hose if you find any.

Step 2) Check the operation of the DPFE with the engine off, key in the run position. Using a digital voltmeter, check for voltage on the brown/light green wire. Look for a reading between .45 and 1.1 volts. If your reading is outside that range, you have one more voltage check to perform before replacing the sensor. Check the voltage on the brown/white wire. It should read 5 volts. If it doesn’t, the sensor isn’t getting power from the computer. Then it’s a whole new ballgame. If you have 5 volts, and the reading from the brown/light green wire is outside the range, replace the DPFE. After replacement, perform the voltage check again to eliminate the possibility that the EGR valve is not seating properly.

Step 3) Leave your meter connected and start the engine. The voltage SHOULD NOT CHANGE! That’s because there should be no EGR flow at idle. If the DPFE voltage changes, either the EGR pintle isn’t seating properly and it’s allowing exhaust flow past the seat, or the DPFE is bad.

 

That's not anal; that's good troubleshooting.

 

Finally got it! (I hope, anyway)
One glaring problem with on-line help forums is that all too often the problem get's solved, with everybody's input, and there is never a final note from the original poster explaining as much. It's too bad because the answere is what we we looking for all along. And a thank you!
In this case it seemed like I went down all the roads and still that **** code kept coming back. Carbon cleaning, testing, hoses etc. Nothing was working.
Last night I was just standing with a beer and looking at at this mess when I noticed an almost imperceptible teeny crack in the front of the DPFE sensor. It only showed because some overspray of PB Blaster had hit the sensor. So again I went to get the electric probes. Sure enough, at idle with cool engine it tested OK. Once I squeezed it, just slightly. the continuity ended. Swapped it out and and I think everything is happy now.
Thanks again all

 

Amen, and thanks for getting back to us, jc.