Subaru Legacy 2002 Service Manual page 1316

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Engine (DIAGNOSTICS)
¼ WIRING DIAGRAM:
B2M4745
No. Step Check Yes No
1 CHECK ANY OTHER DTC ON DISPLAY. Does the Subaru Select Go to step 2. Go to step 3.
Monitor or OBD-II general
scan tool indicate DTC
P0031, P0051 and P0037
at the same time?
EN(H6)-109