DTC P0401: EGR System Insufficient Flow Detected
WARNING: This page is about a different car, the 1998 Acura 2.3CL. However, it is still accessible from the selected car via links, so may be relevant.
Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING CODES under SELF-DIAGNOSTIC SYSTEM. Connect SCS service connector. Test drive vehicle with no electrical load at 55 MPH. Decelerate from 55 MPH for at least 5 seconds. If DTC P0401 does not set, problem is intermittent. System is functioning properly at this time. If DTC P0401 resets, clean intake manifold EGR port and clean or replace EGR valve.