P0174

System Too Lean (Bank 2)

OBD-II diagnostic trouble code P0174indicates a fault detected by the vehicle's onboard computer. This code applies to all OBD-II compliant vehicles and should be addressed promptly to avoid potential engine or emissions system damage.

Severity Level 3 — Moderate

This code indicates a moderate issue that may affect vehicle performance and fuel economy. Continued driving is possible in most cases, but prompt diagnosis and repair are recommended to prevent further damage.

Common Symptoms

• Check Engine Light on
• Rough idle, especially when cold
• Engine hesitation under acceleration
• Whistling or hissing sound from engine bay (vacuum leak)
• Possible P0171 also set (both banks lean indicates a shared cause)

Possible Causes

• Vacuum leak on Bank 2 side of engine — intake manifold gasket, injector O-rings, or vacuum hose
• Dirty or faulty MAF sensor (if both P0171 and P0174 are present, MAF is prime suspect)
• Clogged Bank 2 fuel injectors or low fuel pressure affecting that bank
• Exhaust leak before Bank 2 upstream O2 sensor
• Faulty Bank 2 upstream O2 sensor
• PCV system leak pulling unmetered air (affects both banks)

Common Fixes

• Smoke test and repair vacuum leak on Bank 2 ($100-250 diagnostic, $20-400 repair)
• Clean or replace MAF sensor ($10-300)
• Clean or replace Bank 2 fuel injectors ($80-800)
• Replace Bank 2 upstream O2 sensor ($100-300)
• Replace PCV valve and hose ($30-150)

Estimated Repair Cost

These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.

Explore Repair Costs

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