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

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?

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

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

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

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

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.

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