Comprehensive diagnostic guide for OBD-II P0171 System Too Lean – Bank 1
Quick Answer
What P0171 Means
Your engine is running too lean (too much air, not enough fuel) on Bank 1. This affects performance and can cause engine damage over time.
Most Likely Cause
Vacuum leak or dirty/faulty Mass Air Flow (MAF) sensor
This is the cause in approximately 40-50% of cases
MAF sensor cleaning is easy. Finding vacuum leaks requires some detective work.
Safe to drive, but you may notice reduced power and poor fuel economy. Fix within 1-2 weeks.
Safe to Drive (Short-Term)
Safe to drive, but you may notice reduced power and poor fuel economy. Fix within 1-2 weeks.
$100 - $500
At a repair shop
$10 - $150
DIY (parts only)
Parts You May Need
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Detailed Diagnostic Information
Important Disclaimer
This information is for educational purposes only. We are not licensed mechanics. Always consult a certified mechanic for diagnosis and repair. Improper repairs can be dangerous.
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Last updated: 2025-11-26