P0171Medium Priority
System Too Lean (Bank 1)
Category: Powertrain• Fuel and Air Metering
50 articles · 5 makes affected
What is P0171?
P0171 indicates your engine's Bank 1 is running with too much air and not enough fuel, which is called a 'lean' condition. This is a medium-severity powertrain issue that can reduce fuel economy and performance, and it's commonly triggered by vacuum leaks or faulty sensors. Based on 551 reports, repairs for this code average $4596, with Ford Mustangs and F-150s being among the most frequently affected vehicles.
Common Causes
- ●Vacuum leaks in intake hoses or gaskets (reported in numerous discussion clusters)
- ●Faulty mass airflow (MAF) or oxygen (O2) sensors
- ●Clogged or failing fuel injectors
- ●Fuel delivery issues like a weak fuel pump or clogged filter
Symptoms You May Notice
- ●Check Engine Light is illuminated
- ●Reduced engine power or hesitation during acceleration
- ●Poor fuel economy
- ●Rough idle or engine misfires
How to Fix It
- ●Diagnose and repair vacuum leaks ($150-$500, moderate difficulty)
- ●Clean or replace mass airflow sensor ($100-$300, easy to moderate)
- ●Replace faulty oxygen sensor ($200-$500, moderate)
- ●Service fuel system including injectors and pump ($500-$1500+, difficult)
Root Causesfor P0171
Based on 15 owner reports
Confirmed Causes
- 1misfiring and the cel was flashing(7% of cases)
Common Misdiagnoses
What owners initially thought vs. what actually fixed the problem
- broken,not perfect either(1 reports)
- sure what),cylinder 2 still misfiring(1 reports)
What Didn't Help
Repairs that owners tried but didn't fix the issue
anything seriousbrokenfigure it outgo awayperfect eitherseem to be an air leak in the pipes
Things to Check
Suggested areas to investigate based on similar cases
engine lightengine light is on and i need to renew my registrationis it the same codeproblemthanks for the help
DIY Diagnostic Guide
Tools Needed
OBD ScannerSmoke Machine
DIY Diagnostic Checklist
Based on 15 owner reports
Progress0%
Tools Needed
OBD ScannerSmoke Machine
Step 1check: engine light
Step 2check: engine light is on and i need to renew my registration
Step 3test: and cleaned the maf sensor
Owner Statistics
Based on 964,309 real owner discussions • 28238 confirmed solutions
$2,472
Average Repair Cost
3%
Success Rate
22%
DIY Repairs
964,301
Data Sources
About This Data
Statistics are aggregated from real owner discussions on Reddit, automotive forums, and YouTube comments. All data is anonymized and represents actual repair experiences reported by vehicle owners.
Frequently Appears With
These codes often appear together in owner reports. Check these if you see P0171.
- P017418 reports
- P03017 reports
- P03006 reports
- P04302 reports
- P04552 reports
- P00182 reports
- P03052 reports
- P01702 reports
Based on analysis of 41 owner reports where multiple codes appeared together.
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FORD
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2010 Mustang
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2010 F-150
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2025 Mustang
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2020 F-150
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2010 Mustang
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2016 Mustang
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2016 Mustang
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2010 Focus
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2020 Mustang
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2010 F-150
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2010 F-150
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2010 F-150
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2020 F-150
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NISSAN
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2010 Maxima
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2010 Maxima
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2010 Maxima
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2010 Maxima
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2010 Maxima
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2010 Maxima
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2010 Maxima
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2010 Maxima
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2010 Maxima
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2010 Maxima
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2020 Maxima
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2020 Maxima
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2020 Maxima
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2020 Maxima
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TOYOTA
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2010 Camry
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2010 Corolla
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2020 4Runner
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2020 4Runner
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2020 4Runner
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