Anyone know what code 403 means?

New here and on my second windstar. The tranny just went on the 95 so I went and bought a 99 at a reasonable price. We needed the dual sliding doors anyway. Anyway, the engine light came on after we had the van for about a week and my code reader says the usual 171/174, but also a 403 code. I cant find what that one is. It doesn't seem to be listed in the code sticky thread either.......unless I missed it. Any help would be greatly appreciated. Thanks.

Welcome to the forums Bunyan, this is what I dug up.

P0403 - Exhaust Gas Recirculation Circuit Malfunction

Do a search thru this forum for EGR Valve and you'll find quite a few posts on how to diagnose and test the different components. From what I've read the EGR is not a high failure item.
My advice... do the Isolator Bolts fix first (codes 171/174) with this walk thru http://leckemby.net/windstar/windstar01.html
That would give you the oportunity to clean the EGR orifices since the whole plenum would have to be removed to get to the Isolator Bolts to replace them. That will give you access and clearance to reach the EGR ports and clean them as they get gunky and clogged with deposits making the EGR not work as supposed to. That might be all you need to clear that problem.
If that doesn't help you, then you'll be able to better isolate the EGR with the Isolator Bolts issues fixed.

P0403....Exhaust Gas Recirculation Control Circuit