P0174 — System too lean (Bank 2)
Same lean condition as P0171, but reported on bank 2.
What it means in plain English
P0174 is bank-2 system too lean. With P0171 together, look for shared causes (MAF, fuel pressure, dual-bank vacuum). Alone, focus on bank-2 intake path and sensors.
Common causes
- Bank-2 vacuum or intake leak
- Shared MAF / fuel pressure problems (often with P0171)
- Bank-2 O2 / A/F sensor issues
What you can safely check
- Note whether P0171 is also stored.
- Inspect visible vacuum lines and the airbox/clamp after the MAF.
Pull the code yourself (disclosed)
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A reusable Bluetooth OBD-II scanner lets you read the code and freeze-frame data before authorizing “mystery” diagnostics. One option: BlueDriver Bluetooth Pro OBD-II scan tool (BlueDriver/Levanta affiliate). Any capable OBD-II reader is fine — this is not required to use Fair Auto Shops.
When to go to a shop
Same diagnostic bar as P0171: smoke test and fuel delivery before parts roulette.
Typical related repair costs (U.S. national averages)
These are related repairs shops may find after diagnosis — not a guaranteed bill for every P0174. Ranges exclude taxes, fees, diagnostics, and your location.
- $274–$381 national average for mass airflow sensor replacement (RepairPal; estimates last updated September 3, 2026; excludes taxes/fees and location; source). Labor $51–$75; parts $223–$306.
- $440–$523 national average for oxygen sensor replacement (RepairPal; estimates last updated September 3, 2026; excludes taxes/fees and location; source). Labor $93–$136; parts $347–$387.
Confirm with testing; dual-bank lean often points upstream of both banks.
Related cost guides: Maf Sensor · Oxygen Sensor
Questions to ask before you authorize work
Use questions before you authorize a repair and how to read a repair estimate. Watch for patterns in spotting upselling.
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FAQ
What should I do first with a P0174 code?
Photograph all codes, note symptoms and whether the light is flashing, avoid clearing data until a shop sees it, then use an independent shop with a clear diagnostic plan.
More check-engine codes
P0420 · P0430 · P0300 · P0301 · P0171 · P0455 · P0456 · P0442 · P0446 · P0128 · P0401 · P0133 · P0113 · P0506 · P0507 · P0700 · P0741 · P0011 · P0325 · P0340 · P0335 · P0101 · P0299 · P0135 · P0440 · P0441 · P0010 · P0500 · P0121
Hub: How to read a check-engine code · Repair cost guides · Affiliate disclosure