P0174 — System Too Lean (Bank 2)
Same condition as P0171 but on bank 2 of a multi-bank engine (V6, V8, flat-six, etc.). When P0171 and P0174 appear together, the cause is usually a shared component such as the MAF sensor or a central vacuum leak rather than a bank-specific fault.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Intake manifold
- Mass air flow sensor
- Fuel pump
- Fuel pressure regulator
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Central vacuum leak (intake manifold gasket, brake booster)
- MAF sensor contaminated
- Fuel pressure low (affects both banks)
Possible symptoms
- Check engine light on
- Rough idle, possible stalling
- Hesitation or hard cold start
- Power loss under load
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Related codes
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.