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P0171

Overview

Code

P0171

Code Type

P

Code Class

P0

System

Engine, Emissions

Severity Level

Medium

Emissions Related

true

Drivability Impact

Major

Diagnostic Protocol

OBD2

Freeze Frame Useful

true

Code Definition

Diagnostic trouble code P0171 indicates that the engine is running too lean on Bank 1

Symptoms

Check Engine Light illuminated; Rough idle; Hesitation during acceleration

Overview applies to this diagnostic code.

Affected Systems

On This Page

  • Code Definition

  • Symptoms

  • Affected Systems

  • Possible Causes

  • Diagnostic Steps

  • Drive Safety Notes​

More Resources

Lean air-fuel mixtures affect combustion efficiency, engine performance, and emissions control

Possible Causes

Vacuum leaks; Dirty or faulty MAF sensor; Low fuel pressure

Diagnostic Steps

1 Review fuel trim data; 2 Inspect intake system for leaks; 3 Check MAF sensor readings; 4 Measure fuel pressure; 5 Verify oxygen sensor operation

Drive Safety Notes

Short-term driving is possible, but prolonged lean operation may damage the engine

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