Subaru 2009 IMPREZA Service Manual page 1361

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK EXHAUST SYSTEM.
NOTE:
Check the following items.
• Loose installation of front portion of exhaust
pipe onto cylinder heads
• Loose connection between front exhaust pipe
and front catalytic converter
• Damage of exhaust pipe resulting in a hole
Check
Is there any fault in exhaust
system?
EN(H4DOTC)(diag)-140
Yes No
Repair the exhaust Replace the front
system. oxygen (A/F) sen-
sor. <Ref. to
FU(H4DOTC)-48,
Front Oxygen (A/F)
Sensor.>