Over the last 3 years I have attempted to find and fix the problem with the EGR. The check engine light is always on, had computer check for trouble codes. MAF and EGR Valve were bad. I have replaced EGR Valve and the Vacuum Solenoid. The car was losing power and using more gas. I replaced the MAF, that fixed it for a week. Then put on the EGR Valve and drove from VA to MI with out problem, then some thing just didn't feel right so I had computer check and just said EGR again over and over. Car seems to run rather rough, always sounds rather loud. Advice?
^+1 with Sam. Probably need to replace the dpfe (egr pressure sensor). Is the code po401 (p1401) or po402? Which engine does your '96 have? 3.0 12v ohv Vulcan or 3.0 24v dohc Duratec? Being a GL, I'm guessing Vulcan?
Go to autozone or somewhere like that and they will read your codes for free. There is no code that is named "EGR VALVE"... There is no way for the computer to know if the EGR valve is bad without adding a bunch of expensive sensors. So the DPFE instead monitors the EGR flow and will set a code if it sees a variation in what the flow should be. The DPFE unfortunately goes bad and will tell you there is a problem with the EGR valve when there is not.
If it is an EGR problem you will get something like P0401 or P0402. Make sure you write them down EXACTLY as P1401 and P0401 are VERY different.
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You might also clean the throttle body where the channels go to EGR valve. Usually full of carbon and prevents operation due to lack of flow to EGR.
First thing I do before throwing parts at it!
Also bad EGR gasket can cause issues!!
Just some thoughts on the cheap~~