P0171 - System Too Lean Bank 1

Repair Importance Level: 3/3

Repair Difficulty Level: 3/3

P0171 Causes

Intake air leaks

Faulty front heated oxygen sensor

Ignition misfiring

Faulty fuel injectors

Exhaust gas leaks

Incorrect fuel pressure

Lack of fuel

Faulty Mass Air Flow (MAF) sensor

Incorrect Positive Crankcase Ventilation (PCV) hose connection

What does this mean?

P0171 Notes

If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replace the air filter and clean the air flow meter. If the problem persists the front oxygen (O2) sensor may need to be replaced.

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What does this mean?

First diagnose P0171 code

Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded terminals.

Cost of diagnosing the P0171 code

Labor: 1.0

P0171 Symptoms

Engine Light ON (or Service Engine Soon Warning Light)

Excessive Fuel Consumption

P0171 More Information

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P0171 Description

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.

In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the Malfunction Indicator Light (MIL) (2 trip detection logic).

P0171 Information for specific makes

P0171 ACURA Fuel Injection System Too Lean Bank 1

P0171 AUDI System Too Lean Bank 1

P0171 BMW Mixture Control System Too Lean

P0171 BUICK Fuel Trim System Lean Bank 1

P0171 CADILLAC Fuel Trim System Lean Bank 1

P0171 CHEVROLET Fuel Trim System Lean Bank 1

P0171 CHRYSLER Fuel System 1/1 Lean

P0171 DODGE Fuel System 1/1 Lean

P0171 FORD Fuel Injection System Too Lean Bank 1

P0171 GMC Fuel Trim System Lean Bank 1

P0171 HONDA Fuel Injection System Too Lean Bank 1

P0171 HUMMER Fuel Trim System Lean Bank 1

P0171 HYUNDAI System Too Lean Bank 1

P0171 INFINITI Fuel Injection System Too Lean Bank 1

P0171 ISUZU Fuel Trim System Lean Bank 1

P0171 JAGUAR System Too Lean Bank 1

P0171 JEEP Fuel System 1/1 Lean

P0171 KIA Bank 1 System Too Lean

P0171 LAND-ROVER System Too Lean Bank 1

P0171 LEXUS Air/Fuel Mixture System Lean Bank 1

P0171 LINCOLN Fuel Injection System Too Lean Bank 1

P0171 MAZDA Lean Air/Fuel Ratio Bank 1

P0171 MERCEDES-BENZ System Too Lean Bank 1

P0171 MERCURY Fuel Injection System Too Lean Bank 1

P0171 MINI Mixture Control System Too Lean

P0171 MITSUBISHI System Too Lean Cylinders 1-4

P0171 NISSAN Fuel Injection System Too Lean Bank 1

P0171 OLDSMOBILE Fuel Trim System Lean Bank 1

P0171 PONTIAC Fuel Trim System Lean Bank 1

P0171 SAAB System Too Lean Bank 1

P0171 SATURN Fuel Trim System Lean Bank 1

P0171 SCION Air/Fuel Mixture System Lean Bank 1

P0171 SUBARU System Too Lean Bank 1

P0171 SUZUKI System Too Lean Bank 1

P0171 TOYOTA Air/Fuel Mixture System Lean Bank 1

P0171 VOLKSWAGEN System Too Lean Bank 1