Subaru 2009 IMPREZA Service Manual page 818

Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
BD:DTC P0400 EXHAUST GAS RECIRCULATION FLOW
1. OUTLINE OF DIAGNOSIS
Detect EGR system malfunction.
Intake manifold pressure (negative pressure) is constant because the throttle valve is fully closed during de-
celeration fuel cut. At this time, when the EGR valve is opened/closed, the intake manifold pressure will
change. EGR System OK/NG is judged by the range of this change.
2. COMPONENT DESCRIPTION
(1)
(4)
(1) ECM
(2) Detecting circuit
(3) Switching circuit
(2)
(3)
(4) CPU
(5) EGR valve
GD(H4SO)-94
(7)
(6)
(5)
(6) Main relay
(7) Battery power supply
EN-02192