Content Summary : All Subaru vehicles manufactured since 1996 are equipped with a second genera- tion on-board diagnostic system (OBD II), as required by government regulations.The emissions warranty for many of these vehicles has ended, and some are findingtheir way to independent repair shops for emissions system repairs. While the implementation of the OBD II standards was intended to bring a level of standardization to emissions diagnostics and repairs, vehicle manufacturers andindividual vehicles will continue to have unique design characteristics and repairtechniques. This article offers a collection of repair tips and tricks collected from thefield, focused on late model Subaru emissions system diagnosis, service and repair. EGR Flow Malfunctions OBD II diagnostic trouble code (DTC) P0400 indicates an exhaust gas recirculation flow malfunction. It’s important to keep in mind that this is a functional check of theEGR system. A P0400 DTC usually does not indicate an electrical fault, but rather afailure of one of the components in the EGR system.