I have a 1996 Ford Explorer V8 5.0 AWD and the check engine light was on and it said the following.
P0401 EGR Flow Insufficient Detected
P0402 EGR Flow Excessive Detected

I first took the EGR off and cleaned all the carbon out. It was stopped completly up. I cleared the computer and drove it and light came back on. Then I got this code.

P0402 EGR Flow Excessive Detected

First thing I replaced then was the EGR Valve Position Sensor on the EGR. Reset computer drove it came back up. So I took that off and put my old one back and replaced the EVR because the 96 explorer with 5.0 said it doesnt have the DPF sensor. The EVR is like the DPF and it came up with same error after replacing that. So now its back to the EGR. The EGR seems to work fine however the vacuum line that connects to the EGR doesnt have vacuum to it? Does it only have vacuum with it needs it or is that the problem no vacuum. Does it only sucks the vacuum when the computer tells it to? I sucked on the EGR vacuum line and the EGR doesnt have a hole or anything in it. The truck runs like a dream no miss what so ever but i cant get the check engine light to go off. everytime i reset it comes back.

P0402 EGR Flow Excessive Detected

Is there a way to test the EGR valve? Should it have vacuum to the EGR at all times? Like I say the engine runs fine no miss so what could it be?

 

On the EVR it has 2 hoses and a plug. The bottom hose does have vacuum coming from intake. So im guessing the EVR lets the EGR get the vacuum when it needs it. When i unhook the vacuum line from EGR and suck the EGR open the engine idles way down almost dies and as soon as i let off it bounces back to normal idle. So why is my check engine light on? The EGR seems to be working fine and i have good vacuum.

 

I have a 96 Explorer with a V8 and had the same problem. First the 0401 code (EVR bad) shows and if left unattended it will cause the EGR to get carbon build up and set the 0402 code. The EGR itself still has carbon holding up the pin on the EGR postion sensor thus telling the computer that the pin is in the open position. You will have to remove the EGR and clean it. It took me a few hours to clean it by using penetrating oil and Berryman's B12 spray. I used a vacuum pump to move the EGR up and down while applying the sprays. Before removing the EGR, you can read the voltage of the middle wire (I believe) of the EGR position sensor (key on engine off) for a voltage. It needs to be below .67 volts (I believe this is the voltage but maybe someone could verify) to function properly. If a higher voltage is read, it triggers code 0402. Once I took the valve off, I measured the resistance of the EGR postion sensor (I think it needs to be around 460 ohms when the EGR valve is clean) then continued measuring it as I cleaned the valve. This way I didn't have to continue to hook the valve up to the Explorer. Or you could just buy a new EGR.

 

ok i will remove the EGR and clean it again. Looks to me if it was open and letting air pass it would miss. maybe its just barely letting a little air pass just enough to set the code? i know if the EGR was hung open it would have rough idle.

 

Is code PO402 mean the position sensor is being held back some or could it be other things. Could i not take the position sensor off and grind just a little off that needle that sets against the EGR valve so that it will think its all the way shut? like i say the motor runs fine no miss at all. i crank the motor up and rev it up watching the EGR above idle and it opens and closes and looks as if it works fine. Maybe there is just a little carbon still on it ill try to get it back off and clean it again when i get a chance. only reason im trying to fix it is because it wont pass the emission test on state inspection. check engine light been on and engine runs fine.

 

Yes, you could grind the end off. I would take only enough to get the light to go out just in case some day down the road the carbon is cleaned out and the EGR seats all the way closed. This way you won't set the 0401 code for insufficient flow.

 

im going to try to clean it out again tomorrow and see if that will fix it but if it doesnt im going to grind a little off the pin on the position sensor. it may have just a little carbon in there where the needle is holding it back some i hope. i just need that light off so it will pass inspection.

 

Took the EGR off again and cleaned it the best i could. The EGR is working fine i applied vacuum to it and has no leaks. The pin is sealing up good with no leaks and put it back on and i got the same thing after i drove it about 15 miles. P0402 EGR Flow Excessive Detected. Has new EVR and new position sensor. What is causing this to come up? I rev up the engine above idle and the EGR opens and closes fine its not sticking at all. What else can I try to do to get the check engine light to stay off? I cant get it inspected due to the check engine. It has no miss what so ever just comes up with same error after about 15 miles of driving after reset the computer.

 

This was the same thing I experienced. The EGR was sealed everything seemed okay but the light kept coming on. So I continued to monitor the resistance of the EGR position sensor as I cleaned it. It took a few hours of cleaning and then all of a sudden the resistance dropped (meaning the carbon was gone and the EGR seated completely). There is no way to tell when the valve seats all the way. Only the resistance of the EGR valve postion sensor can tell you since the height of the position needle is porportional to the resistance. If you can measure the voltage on one of the three wires (with EGR on the vehicle) it will tell you how close you are. If you reach a voltage below .67 volts then the light will stay off.

 

which wires do i test? Do you test the wires hooking up to the EGR position sensor? what do you mean by you tested the OHMS on the position sensor while EGR was off. How did it read anything not hooked up? what is the best tools to use to clean the carbon out from behind that needle? i can suck the needle back with vacuum but the hole is so small i don't know what to use in there to clean the carbon out. I just used a small knife and carb cleaner. Where is it sticking at the needle or is there carbon build up inside there that's holding the diaphragm back some? I'm almost ready to just buy a new one but advance auto the one it calls for is different than mine. I haven't checked autozone.

Should the position sensor barely touch the EGR or should it not touch it at all while EGR is closed? I know what your saying when i put the position sensor on it touches a little and i have to push the position sensor down which is pushing the needle in some. should it be flush fit or not touch at all?

 

I used a multimeter. One that does DC voltage and measures resistance. You will need a sharp meter probe to pierce the wire of the EGR postion sensor. Connect the black lead of the meter to the battery negative side (don't use chassis ground). Next use the sharp meter probe red to pierce either the gry/red or Org/yel wire (there are 3 wires coming out of the EGR position sensor). With the key on engine off, you must find the wire showing around .65 volt DC. The other wire will show 5V and another will show 0 volts (ground). Above I said it should be around .67 Volts DC to pass but I think it may be around .58V but I'm not sure (this voltage was given to me on a question I had on this same problem a while back). While probing the wire you can pull vacuum on the EGR and see the voltage rise. Now for checking resistance, since the EGR and sensor were off the car I didn't want to continue to connect the EGR to the vehicle after each cleaning. So, I measured the resistance with the meter (ohm setting) at the spot where the connector is removed. Not sure which two pins (at the connector) I used coming off the EGR sensor. The resistance will change as the EGR moves with vacuum. I wrote down the resistance and went to work on cleaning it (not an easy task) until the resistance changed by a 100 ohms or so. I explained what I used for cleaning earlier in this thread. I squirted in all the openings and where the needle seats. Mine looked really clean but the resistance did not change. But after a few hours spraying and letting the penetrating oil sit, it finally seated all the way. It has worked fine since. I'm still not sure if the seat had carbon or if the pin for the diaphram caused the problem.

The sensor should touch the EGR. You can take the sensor off and check the voltage and resistance to see the difference between off and on of the EGR valve.

 

So you just used the sprays and nothing to scrap the carbon loose. I'm going to buy some of the sprays you mentioned and I'm going to tear it back off again tomorrow and try to clean it. I don't have a meter to check the voltages so i'm gonna just clean, clean, clean. The check engine light doesn't come on until i turn the vehicle off and start it back. I drove it about 100 miles thinking i fixed it and i turned it off then after i crank it i drove it about 15 miles and light came right on. Has it checked again said EGR 402. I will let you know if that fixes it when i get it off and get it cleaned good. Thanks for all the info and help.

 

I did some scraping along with the sprays. Without a meter, I'm not sure you will know when the EGR has completely seated. You may want to let the penetrating oil sit there for an hour or so to help break up the carbon. I'm not really sure what finally cleaned mine. I just know the meter saw a change and then no more light.

The computer has a cycle time in it. So if the light goes off it will not look for the error until the next cycle. The cycle time is around 45 minutes of driving. Also, The computer needs to complete one full cycle with no error codes before it will pass smog. They did this so you could not clear the codes and then get a smog right away.

Good luck and let me know how it goes.

 

I took it back off cleaned and cleaned and scrapped and it never did move any from what i could tell. before i started cleaning it today i took the position sensor off and just fitted it up there to the egr and looked at how much of a gap was in there so i could tell how far the needle was pushed in when i tightened it down. It was the same a gap about as wide as 2 Cd's stacked. i took the position sensor off and ground it down so that it had a gap of about 1 CD thick so that's how far the position sensor pushes in when i bolted it back on. fixing to go drive it i will let you know.

(i ground off my old position sensor so if this doesn't work i still have the new one i bought. and if it works i will return the new.)

If the light comes on now I'm buying new EGR i have spent $128 in my time trying to clean it and that's the price of it at auto zone.

 

well after driving it all day a total of 64 miles the check engine light came on. i took it to advanced they scanned it said...

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction

i put a new gas cap on it and had them clear it and the light came back on. had this.

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction
P0133 02 Sensor Circuit Slow Response (Bank 1 Sensor 1)

could the position sensor be causeing this or is there something else wrong. I have a small exaust leak on the right side header is cracked under the heatshield but when it warms up doesnt leak at all. Bank 1 sensor 1 is the driver side front O2 though. Any suggestions? Could the position sensor i grinded down be causing this?

When I bought the vehicle the check engine light was blown and I drove it for a year like that. When I read the computer after a year it came up with this... PO446, PO133, PO153, PO156, PO401, PO402

I cleaned the EGR and all codes cleared and didn't return except for code PO402. So I'm guessing there's other problems with it other than the EGR.