System Too Lean (Bank 2)
Common Symptoms
- Check engine light on
- Rough idle
- Hesitation under acceleration
- Poor fuel economy
- May set alongside P0171
Most Likely Root Causes
- Vacuum leak on Bank 2 side of intake
- Single MAF sensor affecting both banks
- Fuel delivery issue affecting all cylinders
- Faulty Bank 2 upstream O2 sensor
- Exhaust leak near Bank 2 O2 sensor
- Clogged Bank 2 fuel injectors
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Severity / Derate Risk
Moderate — same as P0171. Dual lean codes indicate systemic issue.
Component Location
Bank 2 = opposite side from cylinder #1. Upstream O2 sensor in Bank 2 exhaust manifold or downpipe.
Manufacturer Notes
P0171 + P0174 together almost always point to MAF sensor or fuel pump, not individual bank components.
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