What is the official meaning of P0174?

The official meaning of P0174 is: System Too Lean Bank 2.

Does P0174 mean the engine is getting too much air or not enough fuel?

P0174 indicates Bank 2 is lean, which can result from too much unmetered air entering the engine, not enough fuel being delivered, or feedback/input information that causes the control module to under-fuel or interpret Bank 2 as lean.

What scan tool data is most useful for diagnosing P0174?

The most useful data includes freeze-frame information and live STFT/LTFT for Bank 1 and Bank 2, along with upstream sensor readings and engine load/airflow parameters. Comparing Bank 1 to Bank 2 trims at idle and at elevated RPM helps narrow whether the issue is a leak, a fuel delivery concern, or a bank-specific fueling imbalance.

Can P0174 be caused by an exhaust leak?

Yes. An exhaust leak upstream of the Bank 2 upstream feedback sensor can allow outside air into the exhaust stream, which can bias the sensor signal lean and drive the module to add fuel until it reaches the correction limit, resulting in P0174.

What should be done after repairs to confirm P0174 is fixed?

After repairing the verified cause, clear codes if appropriate, then run the engine under conditions similar to the freeze-frame data while monitoring Bank 2 fuel trims. Confirmation includes stable trims within a normal range for the vehicle, no return of P0174 (stored or pending), and successful completion of relevant readiness monitors per the applicable drive cycle.

P0174 – System Too Lean Bank 2 — Symptoms, Causes & Fix

P0011 "A" Camshaft Position - Timing Over-Advanced (Bank 1)
P0014 Exhaust "B" Camshaft Position - Timing Over-Advanced (Bank 1)
P0128 Coolant Temperature Below Thermostat Regulating Temperature
P0171 System Too Lean (Bank 1)
P0300 Random / Multiple Cylinder Misfire Detected
P0420 Catalyst System Efficiency Below Threshold (Bank 1)
P0455 Evaporative Emission System Large Leak Detected
P0506 Idle Air Control System RPM Lower Than Expected

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