The check engine light on my 97 f150 4.6 is on. The code checked as low flow EGR. Changed EGR valve still have problem. Removed tube going to exhaust blew it out with air hose and water hose. I still have the same code. If I run extended run on highway light will go out for a day or 2 and then return. Can somebody help?

 

Most likely your DPFE sensor is bad.

 

By the way, after changing the valve, did you clear the code? The light won't go away until its cleared. Just double checking.

If so, then DPFE.

 

There seems to be 3 common problems causing p0401's with the 4.6 and 5.4

On a 4.6L the EGR ports in the throttlebody turndown tube clog up.. You have to take the throttlebody off to see the ports.. This is a very common problem and cheap to fix, just labor if you are careful with the gaskets.

DPFE sensors go bad. 4.6 and 5.4

The vacuum supply line to the egr control solenoid rots and cracks right behind the battery.

Do a search on P0401 and you will be returned with a multitude of interesting threads.

The cracked vac lines is what got my wifes 5.4 expy.

 

THe DPFE SENSOR CONTROLS THE VACUUM TO THE EGR VALVE AND NEEDS TO BE REPLACED HAD THE SAME PROBLEM,,,,,IT IS LOCATED NEAR TO THE EGR VALVE NEXT TO THROTLE BODY ATTACHED WITH 2 SCREWS AND HAS 2 VACCUUM LINES GOING TO IT nd ond 3 prong plug. I PAID $86.00 FOR MINE PROBLEM SOLVED......GOOD LUCK

 

Thanks for the info I am going to try the sensor . The parts guy at the local dealer said he needed the numbers off the sensor that there were 2 different ones. I haven't got the numbers yet . Thanks again for the help.

 

As already pointed out, there are multiple causes of this code.

Since the original poster has already wasted time and money replacing the EGR valve (no troubleshooting performed), it's not particularly useful to suggest replacing yet another part without having done the proper diagnostics.

Just because it fixed the problem on your truck does not mean that it will fix his. It might, but a few simple diagnostic steps will determine the proper course of action and reduce wasted time and money.

Steve

PS. Please hit your CAPS LOCK key....

 

I found this while looking around:

"The Delta Pressure Feedback EGR Monitor is a series of electrical tests and functional tests that monitor various
aspects of EGR system operation.
First, the Delta Pressure Feedback EGR (DPFE) sensor input circuit is checked for out of range values (P1400
P1401). The Electronic Vacuum Regulator (EVR) output circuit is checked for opens and shorts (P1409).


Note: EGR normally has large amounts of water vapor that are the result of the engine combustion process. During
cold ambient temperatures, under some circumstances, water vapor can freeze in the DPFE sensor, hoses, as
well as other components in the EGR system. In order to prevent MIL illumination for temporary freezing, the
following logic is used:
If an EGR system malfunction is detected above 32 oF, the EGR system and the EGR monitor is disabled for the
current driving cycle. A DTC is stored and the MIL is illuminated if the malfunction has been detected on two
consecutive driving cycles.
If an EGR system malfunction is detected below 32 oF, only the EGR system is disabled for the current driving
cycle. A DTC is not stored and the I/M readiness status for the EGR monitor will not change. The EGR monitor,
however, will continue to operate. If the EGR monitor determined that the malfunction is no longer present (i.e., the
ice melts), the EGR system will be enabled and normal system operation will be restored.


After the vehicle has warmed up and normal EGR rates are being commanded by the PCM, the low flow check is
performed. Since the EGR system is a closed loop system, the EGR system will deliver the requested EGR flow as
long as it has the capacity to do so. If the EVR duty cycle is very high (greater than 80% duty cycle), the differential
pressure indicated by the DPFE sensor is evaluated to determine the amount of EGR system restriction. If the
differential pressure is below a calibratable threshold, a low flow malfunction in indicated (P0401)."


.

 

Thanks again for the info I done a voltage check on the DPFE as per Haynes manual. I had reference voltage but no voltage encrease on signal voltage with warm motor and engine reving in gear. Replaced sensor so far so good will have to drive a few days to make sure .