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Code P0171

Symptoms

• Check Engine Light is on

• Poor fuel economy

• Rough idle

Common Causes

• Vacuum leaks

• Faulty mass air flow (MAF) sensor

• Clogged fuel injectors

Glossary

ECM: Engine Control Module

MAF Sensor: Mass Air Flow Sensor

Related Codes

• P0174

• P0101

Official description

System Too Lean Bank 1

Laymans terms

Your car's engine is not getting enough fuel on one side, so it can't run properly. It's like trying to run a race without enough energy.

Explanation

The engine control module (ECM) has detected that the air-fuel mixture on bank 1 is too lean, meaning there is too much air and not enough fuel.

Technical description

P0171 indicates that the fuel system is running lean on bank 1, which is the side of the engine containing cylinder number 1. This is often due to an imbalance in the air-to-fuel ratio, where there is more air than fuel being burned in the combustion process.

Diagnosis steps

• Check for vacuum leaks

• Inspect the MAF sensor

• Examine fuel injectors for clogs

Repair procedures

• Fix any vacuum leaks

• Clean or replace the MAF sensor

• Clean or replace fuel injectors

Tools required

• OBD-II scanner

• Vacuum gauge

• Fuel injector cleaning kit

Estimated repair cost

$100 - $300

Difficulty level

Moderate

Commonly affected vehicles

• Toyota Camry

• Ford F-150

• Honda Accord

Preventive measures

• Regular maintenance checks

• Timely replacement of air filters

• Use quality fuel

Error code type

Engine Performance

User experience recommendations

• Do not ignore the Check Engine Light

• Have your vehicle inspected by a professional

• Regularly maintain your vehicle to prevent recurrence

Warranty information

Check with your vehicle manufacturer for warranty coverage on engine components.

Historical data

P0171 is a common code that has been reported frequently in vehicles with high mileage or those that have not been maintained regularly.

Urgency level

Moderate – Should be addressed soon to avoid potential engine damage.

Legal and safety notice

Driving with a lean condition can lead to increased emissions and potential engine damage.

Testing conditions

• Engine at operating temperature

• Vehicle in closed loop mode

Component location

Bank 1 is typically the side of the engine with cylinder number 1, often found on the driver's side in a V-type engine.

FAQs

Q: What does 'lean' mean in car terms?
A: Lean means there is too much air and not enough fuel in the engine's air-fuel mixture.

Q: Can I drive with a P0171 code?
A: It's possible to drive, but it's not recommended as it can lead to engine damage over time.

Last updated: Oct 28, 2025 • Source: internal database
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