P0174 Code: System Too Lean (Bank 2)
Bank 2 of the engine is running lean — too much air, or too little fuel, in the mixture. It is the bank-2 twin of P0171, seen on V6/V8 engines.
What this means for driving
Same posture as P0171: usually drivable short-term, but lean running over time risks overheating, misfires, and catalytic converter damage. If the engine is stalling, hesitating badly, or running very roughly, have it assessed promptly.
When in doubt, have a mechanic assess it promptly. If any of the red-flag symptoms below are present, stop driving and arrange a tow rather than risking it.
Important: This page is general information only — not professional mechanical advice and not a diagnosis for your specific vehicle. Fault causes and severity vary by make, model, year, and condition. A qualified mechanic should confirm any diagnosis before you make driving decisions or authorize repairs.
Red-flag symptoms: stop and get help
- Engine stalling, especially at idle
- Severe hesitation or loss of power
- Engine overheating
- Check-engine light flashing
Symptoms of P0174
- Check-engine light on
- Rough idle
- Hesitation on acceleration
- Engine stalling
- Poor fuel economy
- Lack of power under load
Most likely causes, ranked
- Vacuum leak affecting bank 2 — hose, intake gasket, or connection
- Dirty or faulty mass airflow (MAF) sensor
- Weak fuel pump or restricted fuel filter
- Clogged fuel injectors on bank 2
- Exhaust leak before the bank-2 oxygen sensor
- Faulty oxygen sensor
How a mechanic diagnoses it
- Fuel trims compared bank-to-bank — if only bank 2 is lean, the cause is usually bank-2-specific (leak, injector) rather than shared (MAF, pump).
- Intake and vacuum lines smoke-tested for leaks.
- Fuel pressure and MAF readings checked.
Likely fixes
- Repair vacuum leak
- Replace MAF sensor
- Replace fuel pump
- Fuel injector cleaning or replacement
Repair costs vary by vehicle, region and shop. Get a quote from a local mechanic.
Related codes
- P0171: System Too Lean (Bank 1)
- P0300: Random/Multiple Cylinder Misfire Detected
- P0420: Catalyst System Efficiency Below Threshold (Bank 1)
CheckMyCarCode content is general information only and is not a substitute for professional diagnosis. Trouble-code meanings are standardized for generic (P0xxx) codes, but causes, severity, and repairs vary by vehicle. If your car shows a red-flag symptom, stop driving and get professional help.