P0174 – System too lean – bank 2
P0174 reports a lean fuel-control condition on bank 2. An important distinction is whether this bank is affected alone or P0171 also reports a problem on bank 1.
Powertrain · Air-fuel control
Open this code in the decoderMeaning and affected system
The bank reference identifies the monitored area. Bank 2 is the cylinder bank other than the one containing cylinder 1; it cannot universally be labelled left or right. Vehicle documentation establishes its location and the sensors assigned to it.
Possible causes
- An intake or ventilation-system leak may admit additional air.
- Incorrect mass airflow measurement can affect both banks.
- A bank-2-only finding also calls for examination of inputs and components assigned to that bank.
Possible symptoms
- A warning light may appear without an obvious change in driving behaviour.
- Uneven running or combustion misfires are possible accompanying findings, rather than symptoms guaranteed by P0174.
Useful diagnostic considerations
- Record short- and long-term fuel trims on both banks under comparable conditions.
- With both P0171 and P0174, consider which air and fuel paths serve both sides.
- For a one-bank finding, confirm the bank identification before interpreting sensor or connection checks.
What this code does not prove
Two lean-bank codes do not automatically mean two faulty oxygen sensors. A single bank code does not conclusively exclude a shared influence either. The pattern guides investigation; it does not replace it.
Related fault codes
Sources and interpretation
This explanation was editorially cross-checked against the technical sources below. Manufacturer documents concern particular vehicle applications; their thresholds and repair procedures must not be applied universally.
- General Motors: P0171 / P0174 engineering information (2017)
- Delphi: Making sense of your sensors — MAF sensor
- Ford: 2013 MY OBD System Operation Summary for Gasoline Engines
OBD-II code data: OBDex (CC0 1.0) · 196fddffb6ef
Editorial source review: .
The causes listed are possibilities without a likelihood ranking. This page cannot replace diagnosis of the vehicle. A code alone confirms neither a failed component nor that continuing to drive is safe. The actual condition, warnings, handbook and applicable manufacturer diagnostics determine the next step.