How can you find and fix an EGR flow malfunction on a '96 Galant?

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.