1998 Chevy Lumina EGR valve/replaced. Check engine light sti

Hi guys. Took me a while to get the code you requested. Here it is--P-0401. It reads egr insuficient flow.W

We both know that's not the problem, as I said 2 new ones were put on. HOPE YOU CAN HELP. THANK-YOU.

If you're sure the intake manifold port is no longer plugged up (and I've seen them plug up again after relatively few miles) two other possibilities remain: (1 -- most likely) Whatever EGR control system this car has has failed. All in some way monitor engine back pressure to modulate the vacuum to the EGR for engine load conditions. (2 -- less likely) the exhaust riser itself is plugged with carbon.

Thank you, guys.I will try both, but if the system has"failed"as you said, does this mean Ineed to replace a computer board that controls the egr valve?Thans again.

There are a number of different EGR systems; I only meant that if yours has a backflow transducer, which usually feeds an electronic signal to a solenoid in a vacuum modulator in turn connected to the EGR, that part of the system can cause problems. But now that I look it up, I think you may have what GM calls a digital EGR, which apparently (I haven't worked on one) gets its signal directly from the computer, which, as docfixit says, reads the manifold absolute pressure from its sensor (on the back of the manifold. I should think replacing the computer would be a costly last resort and therefore only if indicated by a scan readout.