I am getting a P0402 EGR "A" Flow Excessive How to find exact cause

ALso I did a road test with vac gauge attached. At acceleration it would read between 5 -9 inHg vacuum. At WOT no vac and at no throttle no vac. This seem correct unless the value should be 5 inHg and any higher the modulator is at fault. Please let me know the correct vac reading. Thanks

If you pull a vacuum on the valve with a hand vacuum pump and then release the vacuum does the egr valve stick open?I also posted the trouble tree for that code.Let me know what you find.

Thanks I will try.

Your welcome keep me posted.

If you pull a vacuum on the valve with a hand vacuum pump and then release the vacuum does the egr valve stick open? No I did it 5 times(to 20 psi) and it snapped closed each time.

Also on the EGR Modulator, the filter on top was hard side down. I heard the hard/rough side goes up and the soft side down. There was a carbon deposit on the filter that may have plugged the vent hole under the filter. I will try driving for a while and see if the soft side down clears the high flow problem.

Also I tested the EGR temp sensor and got 150KOhms at 89.8 degF measured on the part.This seems ok as it's more than 2500 ohms. I also tested a spare sensor and got 273kOhms at 69.8degF.Which seemed ok.

Also I am confused as to how to carry out the following test procedure. How can I tell if theres restricted flow with the noise of the engine reving to 3500rpm? Is there a trick to it? Thanks

EGR VACUUM MODULATOR
1. Mark vacuum hose locations and disconnect vacuum hoses from EGR vacuum modulator.
See Fig. 26 . Block ports "P" and "R" on EGR vacuum modulator. See Fig. 25 .
2. Apply air pressure to port "Q". See Fig. 25 . Air should flow freely through air filter side
of EGR vacuum modulator.
3. Start and operate engine at 3500 RPM. Repeat test procedures in steps 1) and 2). Strong
resistance of airflow should be felt. Replace EGR vacuum modulator if strong resistance is
not felt. Reconnect vacuum hoses to proper locations.
NOTE: When testing EGR vacuum modulator, it may be necessary to
monitor engine RPM by using scan tester. For scan tester
connections, see IDLE SPEED & MIXTURE in ADJUSTMENTS article.
NOTE: Ports "P" and "R" are the double ports on side of EGR vacuum
modulator. Port "Q" is single port on side of EGR vacuum
modulator

Should I used 30psi air from a compressor and also remove the cap and filter to do the EGR Modulator Test? Is it even worthwhile to do this test? Maybe better to check if filter/port is blocked like I found. I am hoping it was the solution. Thanks.

I would continue on the path your going and see how it turns out looks like you most likely found the problem.Keep me posted.

I drove it 200 miles today and no code. I parked it for 2.5 hours it cooled down and then drove 7 miles no code. That's great it may be solved. Thanks for your help.

I donated $2, I hope you can buy a Mountain Dew with it. Thanks

Thanks for the donation did you donate it to this question?Also how did you know i liked mountain dew?

I don't know if I donated to the question or not. I don't think I saw how to donate directly to the question. How can you?

Problem still exists as of 1:30 PM Friday Oct 19 2012. P0402
After sitting overnight I started it and check lite came on before I was warmed up. I read about this issue, how it throws code before it warms up but I will have to find where. I have the old EGR Modulator, it's ugly but I will switch it tonite and see tomorrow if the code reappears. I replaced the old Modulator with a junk yard pull back in June. I think it may not be the problem since I just started having this code a week ago, but I will switch it back to see. Thanks

Hey Mountain Dew has the most caffiene and I like it too.

I still need help with the EGR Modulator 3500 RPM test, ie how to apply air and to be able to tell it the flow's restricted. Also I will check the hose at the bottom of the Modulator to see if cracked. How does the bottom hose supposed to work? Does it have pressure or vacuum? How much? Thanks

Let me know what happens with the swap.I not sure how to donate on the question we just did a major site grade and relaunch still learning how to make my way around.Also mountain dew is the best i have been drinking it for a long time.I also have a cool light up mountain dew clock from the early 70's.

That clock is cool. Probably worth something to a collector.

I have switched the modulators. The round filter element on top I studied for a while and I think it does go hard side down. There are two little slits at the top of the modulator that would plug up if the hard side was up.
I am going to see if there is vacuum at the EGR valve when the engine is cold also tomorrow. I think it's supposed to be off below 122deg F.That would kind of make sense since the code throws when the engine is warming up.
Thanks

Can you tell me why they say to connect a jumper (in the attached pages)? What does it accomplish? Thanks

Can you please delete the two pages in my previous reply. They may be copyrighted.

OK I let the engine cool down to room temp. Then with vac gauge attached to egr valve vac port, It didn't move at first driving then after temp gauge rose the movement was 3 " Hg vacuum and after it warmed up the same. Last road test I was getting 5-9 "hg on the gauge. Maybe the original(non-junkyard part) modulator works right. I will have to drive it a little bit to see. Also I read that with the P0402 the ECM doesn't turn the light on when it occurs. It waits till the next drive and if conditions are still bad then it throws the code.I think that's why the light came on just as it warmed up previously.My only holdup now is verifying which way the filter goes in the EGR Modulator. It probably doesn't matter though.If the code persists tomorrow, I will check drive test with vac gauge to see if the Hg went up. Thanks.

The original Modulator won't hold pressure on the diaphragm so I switched back with the junkyard modulator and fresh hoses on the EGR system, I could not find a good size hose for the bottom hose but the existing hose is tight and no cracks. Now on road test while looking at Vac gauge the vacuum goes up really hi17"Hg, Then while parked rev to 2500 gives 17"Hg and 3700 RPM gives max of 20"Hg which must be manifold vacuum.Double checked each hose to diagram.

How can I further bench test the EGR Vac. Modulator? Should I ask this in a new question? The new EGR Vac. Modulator is $80 at Autozone and Toyota.Can you guys save me from buying a part when I don't need to? I will donate more if you can. I was thinking of cutting open the orig modulator to see if I can figure out how it works. There's a detailed 4 picture description of it in my Haynes manual. I will study it somemore while waiting for your reply. Thanks

Here is what i have on testing the egr modulator let me know what you find.

Thanks for your reply, I am going to get a new modulator Sunday afternoon. I was worried about how to test the backpressure pipe which connects to the bottom of the modulator. First of all it's really clean, no carbon visible from the top. Then I hooked my vac tester which has a psi scale also. I disabled the EGR valve and ran the engine at 2500 and 3500 rpm, the most backpressure I got was 1.5 psi which I found to equal about 3 inHg in vacuum levels which seems ok. Also I blew about 40 psi compressed air into the small pipe and it did not sound clogged or partially clogged it flowed well. So at this point the junkyard modulator somehow is passing almost manifold pressures to the EGR valve. And my original modulator is cut open to look at, it has a hole in the diaphragm, maybe caused by someone poking a pin into the filter port at some point. Thanks for your help again.

I forgot to add: The only thing I can think of is wrong with the modulator is the spring went bad. Or if somehow it was worked on wrong by cleaning and reaming the pipes or a stiff diaphragm.. Thanks

I was thinking of donating more but I don't know how to be sure it is attached to this question thread. All I see is and Upgrade Question link at the top. Does this button still connect to this question? Did you receive the $2 donation?

Yes i got the first donation thanks you can donate thru the upgrade question.So you found the modulator bad?

Actually the new modulator I got gave me the same vacuum readings as the junkyard one so I returned the new one,I was lucky they took it back. Now I am going to test is the EGR VSV is not passing vacuum when the engine is at less than 140deg F tomorrow morning. If it does allow vacuum to the EGR valve when cold then I will check the thermo sensors, I think there are two(no thermo codes showing). If the vsv does not let vacuum through when cold, I don't know what else I should do. I got a EGR valve from the junkyard today. I may try to install it. I just can't understand how the vac reading from vsv to EGR can be so high coming from the EGR Modulator. At 2800rpm it's 10 inHg and at 3800rpm it's 20 inHg. At 2300-2500 it reads 3 inHg. The vacuum shuts off at idle and Full Throttle like it should. Can you tell me how much pressure should come from the backpressure pipe? I have a manometer I can get working if you can tell the inches of water column it should have. Can you ask your mechanic buddies if they have dealt with the P0402 Excessive EGR flow problem on the 1MZ-FE engine Toyota Avalon or on some Camry's? Thanks

Please look for a $10 donation

Iam not sure about the back pressure pipe yet but my sister has a 1999 ford expedition she had a code for excessive egr flow plus lack of egr flow.She has a back pressure sensor for the egr valve.I found the intake port to the egr valve clogged with carbon behind the throttle body.Cleared the carbon and codes almost a year later still no codes.My question to you is are you sure the intake and exhaust port are clear to the egr valve?I used my sisters expedition as a example that a clogged port can cause the codes to set both ways excessive and not enough.

I removed the EGR valve part way to see if loaded with carbon in June 2012 because of P0401 insuff flow. That code turned out to be the VSV was cracked and leaking not a clogged egr valve. So no other codes till last week P0402 excessive flow which is the issue we are currently looking at. I will remove the EGR valve completely after I get the code to come back after letting the car sit overnite. I think they call this code two-stage because it takes a full two test drives to set. I may take of the egr tube also to check for carbon near the exhaust side.

I don't understand how a clogged port can cause a P0402 Excess Flow. Can you expliain a little bit? On this EGR the temp sensor on the valve seems like the only data the ECM uses to determine flow. Excessive flow means too hot and insuff Flow too cold.

This morning I hooked up my laptop to the DLC connector and used PCMScan to show me the coolant temp so I could see if the VSV allows vacuum to pass when engine is cold. The vsv passed vacuum as though the engine was hot. No difference in vacuum shown hot or cold. I don't know what to do about it. Can you suggest something?

Thanks

You said you had some other codes for temp in a earlier post?So the way i check the egr ports is remove the valve start the engine the rpms should shoot up and you should hear a loud exhaust leak.Iam not sure how to explain a excessive flow code with a clogged port.Untill i saw my sisters set a low flow and excessive flow together with a clogged port i would be thinking the same thing you were thinking about it even being possible.ALso if we go back to the code P0402 trouble tree where does it lead us too?

No I didn't have any other codes this time. I just drove it and no engine light. Maybe it will light tomorrow. Thanks

Keep me posted.

Hi, I am waiting to drive it Thursday to see if the code appears.
I found a list of causes for P0402 and included them here.

How do I detect a sticking EGR valve?

The VSV may have a problem since it works when cold , not supposed to. I have done the checks listed in Trouble Tree and checks out.

The temp sensor seems to have the correct ohm readings. Thanks

Things to eliminate in order:

1 EGR Valve stuck open
I don't want to change this until I rule out why the VSV operates when cold. Can you help me with this?
2 EGR VSV open malfunction
The vsv snaps close at idle and wide open throttle
3 Open in VSV circuit fo EGR
How can the VSV snap close if this is the problem?
4 Short in EGR gas temp sensor
I measured the ohms, seems correct 150 kOhms at 89.8 deg F
5 ECM
This is always the last choice


I just drove it and the P0402 came back while driving, even before warmed up. It had sat overnight.

How do I fix the VSV from opening while cold? I only have 1 working VSV as it replaced the leaking one. Do you think another vsv from the junkyard would work, hey I will just compare numbers. There are a couple vsv's on the car there. I listened to the EGR vsv with a stethoscope and you can hear it cycling, tick tick tick, at low rpm's then the ticking goes away as rpm's increase. Not sure what this means.
How do I fix the VSV from opening while cold?

Thanks for your help

Lets do this i posted a pic of the egr solenoid see if it holds vacuum using a hand vacuum pump.if it doesnt then its stuck open and would explain the egr valve opening when the temp is bellow 140 degrees.Lets try that and go from there.

That's the one I have. The port near the filter is to the EGR Valve. The port by the electrical plug goes to Q port on the modulator. I was just testing it.
At idle on a hot engine the vsv won't hold vacuum at either port. DO I have to drive a little to activate the vsv valve or does this mean I need a new valve? BTW I tested the resistance of the vsv on the car it was 3.41kOhm at 117 deg F. My old leaking vsv was 16.83kOhm and another brown vsv on the car was 45ohms. The book says the egr VSV should be 33-39ohms. What do you think about it? I can try another VOM meter to double check it.

Now that it looks like the vsv should be replaced, how can I be sure this is the case. A lingering doubt I have is should the car be driven to make the vsv close up at idle. I will check on the cost of the VSV at the dealer. Any comments you can make on this to allay my fears would be great.

Another thing I came across was that when the vsv is off, at idle, the EGR valve side opens to the filter on the vsv. While the vacuum from the q port on the modulator is sealed. This makes me think the voltage at the vsv may be suspect. How can I test it? I will test the vsv again unplugged but what if it seals the q port only when energized? How can I test the voltage? Do you have the guide?

Thanks

I just tested the vsv plug with a 12v test light. At idle, the light was initially off, then the first rev it went on and stayed on at idle. Also I plugged it in to the vsv and there was no hold on vacuum at Q port, or egr port. I think the vsv is bad but I am going to test it once more disconnected and with 12v from battery. I got a spare plug from the junkyard. Also my vacuum pump is good and no leaks, I cleaned it a week ago so at least it's not leaky. Thanks, Pete

I ordered the vsv from Toyota. The vsv on the car(which I got from junkyard in June) didn't click when connecting to battery. The original vsv clicks but leaks really bad, cracked. So when it gets here I will let you know the result in a couple days.

Sounds like you found a problem junk parts are great when.theu work.Keep me posted on what happens.

Hi SaturnTech,
The new vsv solved the problem (CEL)! I should have checked if the VSV was clicking by connecting to the battery first.I got the new one from Toyota so I hope it lasts.Thanks for your help. I need to ask a different question, should I make a new question or ask it attached to this one? I donated another $13 so you got a full $25 for this vsv issue. Thanks, Pete

I tried donating the $13 but I get the error "Sorry, the donation amount must be at least $2.00" I will try again later. Will you let the webmaster know this? Thanks

Yes i will let him know thanks for the donations.

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