P0171
System Too Lean (Bank 1)
Description
System Too Lean (Bank 1). This powertrain diagnostic trouble code covers the engine, the fuel and ignition systems, emission control and the transmission.
OBD Codes Details
Possible Causes
Faulty sensor, intake leak, clogged fuel filter, weak fuel pump, damaged wiring
Solution
Check for intake leaks, inspect and clean the sensor, measure fuel pressure, compare live data against the expected range
Symptoms
- Engine runs lean causing rough idle
- Engine may hesitate or stumble during acceleration
- Increased engine temperature
- Poor fuel economy
- Engine pinging or knocking sounds
Diagnostic Recommendations
- Check for vacuum leaks in intake manifold and hoses
- Test Mass Air Flow (MAF) sensor operation and cleanliness
- Inspect fuel pressure and fuel pump performance
- Check oxygen sensor readings and response time
- Examine PCV system for proper operation
- Test fuel injectors for proper flow and spray pattern
Repair Cost Estimate
- Vacuum leak repair: $100-300
- MAF sensor cleaning/replacement: $50-400
- Fuel pump replacement: $400-800
- Oxygen sensor replacement: $200-500
- Total diagnostic and repair: $200-1500
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Fact-checking completed
Verified by:
Pavel Volkov
Created:
Information verified against official sources
Official Sources
Society of Automotive Engineers
Official OBD-II diagnostic trouble codes standard (SAE J2012)
Automotive engineering standards organization
International Organization for Standardization
International standard for vehicle diagnostic systems
International standards for automotive diagnostics
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