P0174 – System Too Lean (Bank 2)
What does P0174 mean?
Bank 2 is running lean — too much air relative to fuel — and the engine computer has reached the limit of its fuel compensation. This is the Bank 2 counterpart to P0171 and appears only on engines with two cylinder banks.
What causes P0174?
Listed from most to least common:
- 1Vacuum leak affecting Bank 2 or the whole intake
- 2Dirty or failing MAF sensor
- 3Low fuel pressure from a weak pump or clogged filter
- 4Failing PCV valve or hose
- 5Clogged fuel injectors on Bank 2
- 6Exhaust leak ahead of the Bank 2 upstream O2 sensor
Code breakdown
Common symptoms
- Check engine light on
- Rough idle and possible stalling
- Hesitation under load
- Reduced fuel economy
How to diagnose
- 1Check whether P0171 is also present — if both banks are lean, look for a shared cause first.
- 2Read long-term fuel trim for Bank 2 to confirm the lean condition.
- 3Smoke-test the intake system for vacuum leaks.
- 4Verify fuel pressure meets specification.
- 5Inspect and clean the MAF sensor.
- 6Check the Bank 2 exhaust for leaks ahead of the oxygen sensor.
Sustained lean running increases combustion temperatures and can damage the converter and internal engine parts over time.
Common fixes and estimated costs
| Repair | Estimated cost |
|---|---|
| Clean MAF sensor | $10–$30 (DIY) |
| Replace vacuum/intake hose | $30–$200 |
| Replace PCV valve | $40–$150 |
| Replace intake manifold gasket | $200–$600 |
| Fuel pump replacement | $400–$1,000 |
Costs are rough US estimates including parts and labor. Actual pricing varies significantly by vehicle, region, and shop rates.
Good to know
P0174 rarely occurs alone. When it does, focus on Bank 2 specific items — that bank's injectors, O2 sensor, and the exhaust ahead of it.
Related codes
This information is provided for general reference only and may vary by manufacturer, model, and year. It is not a substitute for professional diagnosis or repair.