Subaru LEGACY 2003 Service Manual page 106

ENGINE (DIAGNOSTICS)
Symptom
14. Remarks
A*: Including ECM ground circuit
B*: Check hoses.
GENERAL DIAGNOSTIC TABLE
1) ECM power supply
2) Pressure sensor
3) Pressure regulator
4) Idle air control solenoid valve
5) Air leak in air intake system
EN(H4SOw/oOBD)-104
Problem parts Priority
A*
B*
B*
B*
B*