rojo

I just posted more info on a similar thread, but for folks having this problem, here's what my dealer found: There's a Subaru tech tip dated June 2006 about CEL Code P0400 (EGR code). In following the recommended procedure, dealer found the hose connected to the MAP sensor was pulled loose at a "T" in the vacuum line. Cheap fix!

For folks having problems with the check engine light coming on and turning off, pulling P0400 and P0440 codes (and possibly other emissions codes), here's a tip: Our 1998 Forester was having that problem for a couple of years (2004-2006). The dealer replaced EGR valve, Back Pressure Valve, solenoid valve... to no avail. (Check engine light would return within a few to 500 miles, turn off, come on, turn off...) Finally the dealer mechanic called Subaru tech support, and was advised of a tech tip dated June 2006 about P0400 EGR code. He followed the procedure in the tech tip, and found that the hose connected to the MAP sensor was pulled loose at a "T" in the vaccum line. (MAP = Manifold Absolute Pressure.) Reconnected line. Voila! This hose had apparently jiggled loose (or been disconnected?) during a clutch job 2 years earlier. This "T" in the vaccuum line is apparently obscured from sight when everything else under the hood is in place. Don't know how hard it is to access. Just read in Wikipedia that the MAP sensor provides data "used to calculate air density and determine the engine's air mass flow rate, which in turn determines the required fuel metering for optimum combustion." And, "The MAP sensor can also be used in OBD II (on-board diagnostics) applications to test the EGR (exhaust gas recirculation) valve for functionality." Thus the connection between the EGR code and this disconnected hose.