There are three major components in the EGR circuit. First: the EGR valve itself, Second: the Back Pressure Transducer, Third: The EGR Solenoid Valve.
First one should check to see if the ports going from the EGR valve to the exhaust and then to the throttle body/manifold are clear of carbon. Often these ports will fill with carbon and therefore restrict the flow rate from the EGR valve. Once these have been cleaned, you then need to clear the DTC codes and run the drive cycle to reset the computer. If the Check Engine light comes back on and the DTC code re-appears, then you should check the EGR valve itself, this can be done with a simple hand held vacuum pump by connecting the pump to the vacuum port on the valve and with the engine at idle, apply vacuum to the valve. Usually, the engine will "falter" or "sputter" at idle when the valve opens. If this doesn't happen and you don't observe the valve opening, then it is bad and should be replaced. This test is also pretty good in checking those ports mentioned earlier, if the enging does perform as mentioned at idle when the valve is activated with the vacuum pump, the ports are probably ok. The second part to look at tis the back pressure transducer, this is usually a small round device to which the vacuum line from the EGR valve is attached, or often there is a "T" or "Y" fitting with one side going to this tranducer and the other to the EGR valve. You should check this valve to see if it is allowing vacuum thru it, if in doubt replace it. The third item is the EGR solenoid and it will have a vaccum line from it to the EGR valve (or to the "T" or "Y" connecter mentioned before) and a vacuum line to a vacuum port usually found on the throttle body. To test this device, first see if it is getting 12 V to one side of the coil and then make sure the coil is being grounded by the computer when the engine is revved up to around 3000 rpm. If you aren't sure, remove the solenoid, apply a 12 volt DC source to the coil and ground the other coil terminal. You should feel or hear a "click" when you apply the 12 volts, then you should be able to have low pressure air or vacuum flow through the solenoid. If you don't feel or hear the "click" or you can't get any flow through the solenoid, replace it. About 90% of the time one of these will fix the problem of the P0400 code or EGR Flow Malfunction.
Hope this is of some help, Randy A.
change the egr valve
EGR Flow malfunction
P0403 = EGR Flow circuit malfunction.
Plugged EGR passage which restricts the flow of exhaust gasses, faulty EGR solenoid, faulty EGR solenoid wiring/harness, vacuum lines damaged or disconnected to the EGR valve solenoid or to the EGR valve, or a faulty EGR valve.
egr valve is usually on the back side of the engine,2.4l sohc is behind and below the intake manifold . It has a vaccuum line attached and these do crack and break.Also check the egr because they have a rubber diaphragm inside that can crack allowing the vaccuum to leak causing a problem.The other thing is the newer fuels are running the engines so lean that carbon builds up both inside the egr and what the egr port mounts to. Make sure they are both CLEAN!
The EGR Valve on the 1996 Mitsubishi Galant is located underneath the Exhaust Manifold.
well on my 2000 Chevy tracker it is an egr flow malfunction. Girl at autozone said it could be a egr blockage.... Mike
po400 means you have insufficient or excessive exhaust flow within the egr system. The o2 code means it has detected this as well. Chances are both are on because either the egr system is not passing exhaust fumes into the manifolds properly. or the manifold has a leak. You can start by checking the manifold for leaks, cracks, holes, etc. If the manifolds seem tight, try actuating the egr valve. If the egr valve works blow compressed air through the tubes of the egr system and find the leak or clog. Carbon buildup is the number one cause for a clogged egr. Also check the lines make sure they are free of holes and are attached. Dont buy a new o2 sensor until you have fixed the egr code as the egr malfunction will likely set the o2 code again within a few months. hope this helps..
P0400 Exhaust Gas Recirculation Flow Malfunction LIBERTY DOES NOT HAVE AN EGR SYSTEM. P0400 DOES NOT APPLY TO LIBERTY
I would look into a stuck open, or jammed Egr Valve.
Just because a code that is titled to a particular system is noted does not mean that component is bad. Check the passageway.
Normal cause if a failed egr valve.