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2004 Forester X
61 Posts
Discussion Starter #1
so today i got a new code p0171 any ideas what it could be. i also have code 0420 too but i know it the cat

2007 Forester Sports XT 4EAT
38,952 Posts
@Chemically looks like you have lots of possible causes! :icon_eek:

P0171 SUBARU - System Too Lean Bank 1
P0171 Subaru Possible Causes:
• Intake air leaks
• Faulty front heated oxygen sensor
• Ignition misfiring
• Faulty fuel injectors
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel
• Faulty Mass Air Flow (MAF) sensor
• Incorrect Positive Crankcase Ventilation (PCV) hose connection

P0171 Subaru Tech Notes:
• If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replace the air filter and clean the air flow meter. If the problem persists the front oxygen (O2) sensor may need to be replaced.

['07 FSXT MODding Journal] ['03 X MODding Journal]
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