I took my 2003 mercury mountaineer in for a smog check and all was good except my "service engine soon" light is on. The OBD code is po401 (EGR flow is insuficient). I don't know much about the EGR system but I did a visual inspection and did'nt see anything diconected ,etc. Can anyone tell me some likely causes or things to check?
Mar 31, 2009 at 6:26 PM