Question

2005 Subaru Impreza WRX 2.0L with engine code P0171, what do I need to replace?

Answer 1

Hi there,

The most common cause for this issue is the mass air flow sensor, or a problem with the front O2 sensor. I would test these and look for a possible issue with an intake manifold leak as well.

Answer 2

P0171 SUBARU Code - System Too Lean Bank 1
Read more: https://www.autocodes.com/p0171_subaru.html