Code P0402 Excessive EGR flow
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Joined: May 2004
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From: Trappe Pa
The P0401 (EGR flow insufficient) and the P0402 (EGR flow excessive) is indicative / tends to point to the DPFE sensor being the problem. I’d check the sensor as I previously mentioned.
The PCM programming will always want to activate the EGR valve under driving conditions. The PCM therefore will also be looking for a confirmation from the DPFE sensor that the EGR is indeed working.
Removing the EGR vacuum hose to disable the valve will keep the valve from introducing exhaust gas into the intake manifold, but the PCM will know something is wrong because the DPFE signal wire voltage will not change as expected when the EGR is commanded open.
What happens now??? The Check Engine light will illuminate.
The PCM programming will always want to activate the EGR valve under driving conditions. The PCM therefore will also be looking for a confirmation from the DPFE sensor that the EGR is indeed working.
Removing the EGR vacuum hose to disable the valve will keep the valve from introducing exhaust gas into the intake manifold, but the PCM will know something is wrong because the DPFE signal wire voltage will not change as expected when the EGR is commanded open.
What happens now??? The Check Engine light will illuminate.
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Junior User
Joined: Jul 2005
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Spend the $50 or so at NAPA or Autozone and get a new DPFE sensor, it takes all of 5 mins to swap it out. Drive as normal, the light should go out on it's own (mine did). Problem solved and it sounds like a lot less work than your plan.....g/l
Originally Posted by Spiff59
I have a 2002 Escape (is hers, actually) with a 3.0L Duratec. It started reporting both P0401 and P0402 a week ago. It's otherwise running fine. I'm about 99% sure it's a DPFE problem.
I don't think I can count how many EGR valves I bypassed in the old days (it is legal to do so in my state). Just plug the vacuum line, or remove the entire valve and bolt on a block-off plate, and off you go with better overall performance.
I'm inclined to plug the EGR vacuum control line on the Escape, to keep the EGR valve in the closed position, but having the CEL lit all the time would give my old lady ulcers. It would also be nice to have the light still functioning to handle the case of a failure of the oxygen sensor or some other emissions control.
So, disabling the EGR is cake, but how to stop the P0401 and P0402 errors without disabling the Emissions Control dashlight entirely?
Would maintaining 1V on the "return sensor wire" when the ignition is on keep the light off? Regardless of whether the engine is off, or running at any RPM?
Maybe a resistor (what value?) from the 5V lead to the sensor wire would do the trick, or maybe a small DC voltage regulator like the 3-connector LM317? Soldering 5 diodes in series would yeild a 3.5V drop leaving 1.5V to the sensor wire... Any ideas? I'm concerned the voltage on the sensor wire varies under different operating conditions, but am not sure how particular the ECU is before triggering the fault and the error codes.
If I could trash the worthless EGR and have the light working otherwise for a couple bucks, I'm game. Otherwise I guess it's $66 to Ford for a part which likely costs them $3.
Thanks.
I don't think I can count how many EGR valves I bypassed in the old days (it is legal to do so in my state). Just plug the vacuum line, or remove the entire valve and bolt on a block-off plate, and off you go with better overall performance.
I'm inclined to plug the EGR vacuum control line on the Escape, to keep the EGR valve in the closed position, but having the CEL lit all the time would give my old lady ulcers. It would also be nice to have the light still functioning to handle the case of a failure of the oxygen sensor or some other emissions control.
So, disabling the EGR is cake, but how to stop the P0401 and P0402 errors without disabling the Emissions Control dashlight entirely?
Would maintaining 1V on the "return sensor wire" when the ignition is on keep the light off? Regardless of whether the engine is off, or running at any RPM?
Maybe a resistor (what value?) from the 5V lead to the sensor wire would do the trick, or maybe a small DC voltage regulator like the 3-connector LM317? Soldering 5 diodes in series would yeild a 3.5V drop leaving 1.5V to the sensor wire... Any ideas? I'm concerned the voltage on the sensor wire varies under different operating conditions, but am not sure how particular the ECU is before triggering the fault and the error codes.
If I could trash the worthless EGR and have the light working otherwise for a couple bucks, I'm game. Otherwise I guess it's $66 to Ford for a part which likely costs them $3.
Thanks.
Senior User
Joined: May 2004
Posts: 279
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From: Trappe Pa
No offense to anyone but I would recommend checking the DPFE sensor wire voltages first to confirm the sensor is the cause of the EGR codes.
I hate throwing money and parts at the vehicle hoping the problem will be fixed. Throwing parts on the vehicle is the easiest and quickest way to lighten your wallet, especially if the parts don't solve the problem.
I hate throwing money and parts at the vehicle hoping the problem will be fixed. Throwing parts on the vehicle is the easiest and quickest way to lighten your wallet, especially if the parts don't solve the problem.
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Joined: Jan 2001
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Skweeker, thanks for the info. I also have an '01 XLT 4WD V6, and the CEL popped on a couple of months ago. With your info I measured 5.2V on the Brn/Wht, 2.0V on the Brn/Lt Grn, and 0.0V on the Orn, so I guess my next step will be getting and installing a new DPFE sensor. I've seen comments about Ford re-designing the OEM sensor; any idea if the aftermarket makers have made any needed changes?
Also, for any one else, if you have needle tips on your multimeter probes it will be easier to insert them into the back of the wires as Skweeker instructs. I had to turn off the ignition and pull the connector off the sensor for each reading with my probes, plus the fact that the back of the connector faces towards the firewall aslo made it difficult to back probe the connections.
Also, for any one else, if you have needle tips on your multimeter probes it will be easier to insert them into the back of the wires as Skweeker instructs. I had to turn off the ignition and pull the connector off the sensor for each reading with my probes, plus the fact that the back of the connector faces towards the firewall aslo made it difficult to back probe the connections.
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Joined: Jan 2001
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Just a follow up - I found a new sensor at rockauto.com for $25, but being concerned that it might be the old design (which appear to fail prematurely), I checked some local parts store for the YF1E-9J460-AD (the OEM p/n in my '01 XLT). No luck - no one had a replacement. So I schlepped down to the local dealer and for $73 got a 4U7Z-9J460-AA. After installing the new unit, checked the voltages (per Skweeker's info) and everything measured just right (5V, 0V & 1V, respectively).
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From P0401 to P0402, frustrated!!
My wife's 2000 Expedition's CEL came on a while back with P0401. After alot of searching online, most forums had the DPFE as a reoccuring theme. I changed the DPFE myself a few months ago and had the carbon cleaned at a service shop. The CEL P0401 came back about 3 weeks later and stayed on. More research and Haynes had me checking the ohms on the EGR Vaccuum Solenoid and the voltage on the DPFE, both were within spec. So I broke down and replaced the EGR Valve vice cleaning it (my wife would sleep better knowing I replaced it). I thought I saved the day but now the CEL came back on within a day and it's reading P0402. So it went from P0401 before EGR replacement to P0402 after replacement.
What gives?? What else do I need to check/do? I have no desire to put alot of $$$ into the vehicle and I'm definitely not taking it to a dealer.
This is getting old, real fast.
Thanks for the advice and assistance.
What gives?? What else do I need to check/do? I have no desire to put alot of $$$ into the vehicle and I'm definitely not taking it to a dealer.
This is getting old, real fast.
Thanks for the advice and assistance.
Elder User
Joined: Nov 2003
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My wife's 2000 Expedition's CEL came on a while back with P0401. After alot of searching online, most forums had the DPFE as a reoccuring theme. I changed the DPFE myself a few months ago and had the carbon cleaned at a service shop. The CEL P0401 came back about 3 weeks later and stayed on. More research and Haynes had me checking the ohms on the EGR Vaccuum Solenoid and the voltage on the DPFE, both were within spec. So I broke down and replaced the EGR Valve vice cleaning it (my wife would sleep better knowing I replaced it). I thought I saved the day but now the CEL came back on within a day and it's reading P0402. So it went from P0401 before EGR replacement to P0402 after replacement.
What gives?? What else do I need to check/do? I have no desire to put alot of $$$ into the vehicle and I'm definitely not taking it to a dealer.
This is getting old, real fast.
Thanks for the advice and assistance.
What gives?? What else do I need to check/do? I have no desire to put alot of $$$ into the vehicle and I'm definitely not taking it to a dealer.
This is getting old, real fast.
Thanks for the advice and assistance.
IMHO I would suggest if you do not want to take the vehicle to a good mechanic and get it fixed the right way, you trade it in on a different vehicle or just drive it the way it is.
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Joined: Jun 2010
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I'm pretty sure a P0402 is an EGR flow problem, so the tubing might be disconnected, reconnected wrong, pinched, cracked, clogged, carbonized, iced up, or marfed or something. You should verify that the tubing is good, connected right & not clogged. Make sure the metal tube good. I don't recall exactly, but a simple test is to start the engine then disconnect the tubing from the EGR valve - the engine should stumble or stall (pretty sure).
I guess the DPFE sensor could be clogged w carbon: maybe it tests fine electrically, but it's clogged. Also, sometimes electrical components test different when they're hot. Unless the DPFE isn't that old, I would probably go ahead & replace it. If that doesn't do the trick & the tubing isn't clogged... don't know... Double check the tubing then take it to a mechanic?
PS: you might be able to get an old fashioned binder-type of Ford powertrain/emissions troubleshooting manual on ebbaayy for fairly cheap.
I guess the DPFE sensor could be clogged w carbon: maybe it tests fine electrically, but it's clogged. Also, sometimes electrical components test different when they're hot. Unless the DPFE isn't that old, I would probably go ahead & replace it. If that doesn't do the trick & the tubing isn't clogged... don't know... Double check the tubing then take it to a mechanic?
PS: you might be able to get an old fashioned binder-type of Ford powertrain/emissions troubleshooting manual on ebbaayy for fairly cheap.
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DPFE
You have to check the sensor with key on and wiring connected. I checked mine by doing 1. Key on 2.Not running 3. put vacuum hand pump on DPFE inlet that is connected to downstream side of EGR. You should see a voltage change on signal wire to correspond to vacuum. 3.7 in-HG should give full voltage(about 4.7volts DC). On mine I had to put 15 in-hg vacuum to get it to output 4 volts. This proved that the sensor was out of calibration/faulty. If this test is normal, there is also a EGR vacuum relay that actually controls how much EGR is applied. This is basically a relay that is pulsed on and off electrically and it operates the solenoid to control amount of vacuum going to EGR valve.
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20, checkengine, code, codes, egr, error, escape, excessive, f150, flow, ford, p0402, po402, yf1e9j460ad, yfie9j460ad
