P0174 means System Too Lean (Bank 2). The same lean condition as P0171, but on bank 2, the side of a V engine that does not contain cylinder 1. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0174 means
The engine computer keeps adjusting fuel to hold the air-fuel mixture near the ideal ratio, using oxygen sensor feedback. Those adjustments are fuel trims: short-term trim reacts instantly and long-term trim learns over time. Positive numbers mean the computer is adding fuel; negative numbers mean it is taking fuel away. When long-term trim sits near the limit the computer allows, it sets a lean or rich code. On a V engine, bank 1 is the side containing cylinder 1 and bank 2 is the opposite side; inline engines only have bank 1.
P0174 symptoms
- Check engine light
- Rough idle or stumble
- Hesitation under acceleration
Common causes of P0174
- Vacuum leaks on that bank, such as an intake gasket
- A shared cause such as the MAF sensor or low fuel pressure, which usually sets P0171 at the same time
- Leaking or clogged injectors on bank 2
- An exhaust leak near the bank 2 upstream oxygen sensor
How to diagnose P0174
- Note whether P0171 is also set: both banks lean points to something shared, such as the MAF, fuel pressure or a central vacuum leak
- Compare fuel trims bank to bank
- Smoke-test the intake, focusing on bank 2 gaskets and hoses
- Check injectors on that bank
Can you drive with P0174?
Similar to P0171: drivable in the short term, but repair it before lean misfires or heat cause other damage.
P0174 tips
When only bank 2 is lean, look at what is unique to that side: its intake gasket, the injectors on that bank and any exhaust leak ahead of that bank’s upstream oxygen sensor. If P0171 and P0174 set together, start with the parts both banks share; one shared fault, such as a split intake boot, often clears both codes.
Will P0174 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0174 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0171 | System Too Lean (Bank 1) |
| P0175 | System Too Rich (Bank 2) |
| P0101 | Mass or Volume Air Flow Circuit Range/Performance |
| P0300 | Random/Multiple Cylinder Misfire Detected |
Guides that help
- fuel trim explained
- fuel filter
- engine sputtering
- vacuum leak
- MAF sensor symptoms and cleaning
- fuel pump, filter and regulator symptoms
- fuel injector symptoms
When it is more than a sensor
Fuel trim codes are almost always fixed with a leak repair, a sensor or a fuel delivery part. If a long-running lean condition has burned a valve or piston and a compression test confirms it, compare repair against a replacement on our engines page and see engine replacement cost.
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