Code P0400 - EGR Flow
 

Car runs fine, just no EGR flow. Valve operates freely, but I don't have a hand vacuum pump to test for ruptured diaphragm. I guess I should buy one. Valve internals look fine, but crapped up internals would cause the opposite problem (EGR flow when I don't need it due to valve not shutting completely, accompanied by rough idle). With a Fluke attached to EGR solenoid, I get a momentary 12V signal when I punch the throttle, but it only lasts a second or two. I'm assuming that the 12V signal is momentary due to the initial burst of air when I hit the throttle. The ECU "thinks" the engine is under a load in the EGR solenoid operating range, so it energizes the solenoid, but once the initial surge is gone all I've done is increased the engine speed with no real load, so the ECU sees this and de-energizes the solenoid. Anyone know if my reasoning is right? Is the momentary 12V signal when I punch the throttle telling me that the computer side of the EGR system is working properly? The soleniod coil is good. Not exactly sure what the reading should be, but I'm getting 35ohms which seems pretty good. I guess my vacuum control valve could be bad....does anyone have a "Go-No-Go" test for that?

Thanks for the time to read.....

RE: Code P0400 - EGR Flow
 

Model, year and engine would help;)

Joel, CA

RE: Code P0400 - EGR Flow
 

Sorry about that Joel......Galant / 2000 / 3.0L.......

Paul, VA

RE: Code P0400 - EGR Flow
 

To check the diaphram, just hook up a vacuum hose and suck on it. Put your tongue on the tube after you suck and it should hold the vacuum. If not, you have a hole in the diaphragm.[&:]

RE: Code P0400 - EGR Flow
 

If you want to check your EGR system- simply pinch the vacuum hose on the top of the throttle body with the yellow tracer with the engine running. This is the vacuum bleed hose. Blocking/pinching it will eliminate the escape path of the vacuum thus applying vacuum to the EGR valve (causing immediate stumble). With the sensitive emission system on all late model OBDII systems- it's not that you don't have EGR flow, the check engine light is on because you don't have ENOUGH or because you don't have immediateEGR flow.
Most common remedy? Removing the intake hose and cleaning the ports on the top side of the throttle body bore (specifically the EGR source vacuum port- hose with green tracer) usually eliminates the problem. Do this by wiping the bore with a rag soaked with throttle body cleaner. Be sure your getting your fingers deep enough into the throttle body (think back 2 Jr high school ;) ) to reach the ports. If that doesnt do the trick- there is a vacuum restrictor in one of the vacuum lines going to/coming from the vacuum delay valve (hose with white tracer) that can become clogged or partially blocked significantly lowering the amount of available vacuum to open the EGR valve. This part of the EGR vacuum circuit may not be easily seen or accesable. If you are able to access it, you can replace that section of hose with a similar sized vacuum hose eliminating the restrictor altogether.

Of course, you can check the EGR solenoid by applying power and ground to it to see if it works. (this should be done 1st just to eliminate this as a suspected source of failure)

Good Luck!

Joel, CA

RE: Code P0400 - EGR Flow
 

Awesome pointers Joel.....I have a feeling I'll be finding the problem next time I'm under the hood.javascript:void(AddText(':)'))
I'll let you know how it turns out.....

Thanks Much
Paul

RE: Code P0400 - EGR Flow
 

Joel,

Thanks again for your help. Problem solved. When I first pinched the bleeder hose I had a slow, delayed roughening of the idle. Did it again and same thing. I checked the solenoid and it was working fine. Pinched the hose again, and nothing happened. Hmmm.... So I checked all hoses in the EGR circuit, and they were fine. Decided to pull the throttle body, discovered total blockage in the vacuum port in the throttle body. Cleared that out with some stiff wire, cleaned the throttle body internals and went ahead and cleaned the valve seating sufaces of the IAC Valve while I had the easy access (just for fun). Put it all back together and started the car....when I pinched the bleeder hose this time, I had the "immediate stumble" that you described. With the code cleared I took the car for a drive, and was treated to a flashing EGR Monitor icon that went soild when the trip cycle completed.....and as I'm sure you know....that means my repair was confirmed. EGR monitor cycle completed SAT!!!!

Again.....thanks for your help! I learned a lot from your suggestions, and even had fun doing it! Don't be surprised if I tap your knowledge in the future....

Drive Safe (and fast)
Paul - VA

RE: Code P0400 - EGR Flow
 

That's great! A good thing about late model Mitsubishi's is that the drive cycle to complete each monitor is relatively easy to complete ESPECIALLY the EGR Monitor. Not only that, but you just became that much more intimate with your vehicle. Things will start to get much easier for you from here!

Joel, CA

Egr p0400
 

Hi im having a p0400 issue with my car, and getting low mpg on a mirage 98.
I have found this forum and follow recommendations and was very helpful but my car still turning on the check engine light.

I have cleaned the intake manifold.
replaced egr valve (new one)
solenoid (new)
replaced cracked hoses (new)
Coolant Sensor (new)
Intake Air temperature sensor (new)
Removed throttle body and cleaned all the vacuum lines
Catalytic (New)
O2 sensors (new)

And still getting Check engine light

There is a vacuum diagram for my car.

If someone knows something, any help will be appreciated.