P0171: System Too Lean (Bank 1)
P0171 is an OBD-II diagnostic trouble code meaning “System Too Lean (Bank 1).” The engine is running lean on Bank 1 — too much air or not enough fuel. One of the most common OBD-II codes across all makes. According to Au7o's database, this code appears across 177 vehicle models from 20 manufacturers. Full vehicle-specific causes and solutions at au7o.io.
Common Causes
Diagnostic Tools
To diagnose P0171, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Vehicles Affected by P0171
Click any vehicle to see the full issue details, symptoms, and repair guide.
Related Codes
Frequently Asked Questions
What does P0171 mean?
P0171 stands for "System Too Lean (Bank 1)." The engine is running lean on Bank 1 — too much air or not enough fuel. One of the most common OBD-II codes across all makes.
What are the most common causes of P0171?
The most common causes of P0171 are: Vacuum leak (intake gasket, hoses, PCV), Dirty or faulty MAF sensor, Weak fuel pump, Clogged fuel injector, Exhaust leak before O2 sensor. The specific cause varies by vehicle — Au7o documents vehicle-specific causes for 177 models.
How much does it cost to fix P0171?
Repair costs vary widely depending on the root cause and vehicle. Check the vehicle-specific issues below for estimated costs.
Which vehicles are affected by P0171?
Au7o has documented P0171 across 177 vehicle models from 20 manufacturers: Audi, BMW, Cadillac, Chevrolet, Chrysler, Dodge, Ford, GMC, Honda, Hyundai, Jeep, Kia, MINI, Mazda, Nissan, RAM, Subaru, Toyota, Volkswagen, Volvo. See the full list below for vehicle-specific causes and repair costs.
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