P0400 Exhaust Gas Recirculation Flow Malfunction. This can be many things. I would start by cleaning the EGR valve throughly and checking all EGR vacuum lines. If you have already done this then it may be time to take it to a pro before you spend more money needlessly. or http://carfix.stufftoread.com/EFI-1.html free advice no ads !
P0400 is an EGR code. Usually caused by carbon blocking some of the the vacuum ports. It can also be caused by a blocked vaccum hose, misrouted hoses, or even a bad ECM
P0400 Exhaust Gas Recirculation Flow Malfunction LIBERTY DOES NOT HAVE AN EGR SYSTEM. P0400 DOES NOT APPLY TO LIBERTY
Trouble code P0400 means: EGR System Performance
Trouble code P0400 means:Exhaust gas recirculation flow malfunction
Trouble code P0400 means:Exhaust gas recirculation flow malfunction
Trouble code P0400 means:Exhaust gas recirculation flow malfunction
Trouble code P0400 means:Exhaust gas recirculation flow malfunction
Trouble code P0400 means: EGR System Performance
Trouble code P0400 means:Exhaust gas recirculation flow malfunction
Trouble code P0400 means: Exhaust Gas Recirculation Flow
Trouble code P0400 means:Exhaust gas recirculation-flow malfunction
Trouble code P0400 means:Exhaust gas recirculation flow malfunction