P0174 — System Too Lean (Bank 2)
Moderate severityWhat it means
The mixture on bank 2 is too lean, so the engine control unit is adding maximum fuel correction. When P0171 and P0174 appear together on a V-type engine, the cause is almost always shared — a vacuum leak or a faulty MAF sensor rather than a bank-specific part.
Common symptoms
- Rough idle or hesitation
- Hard starting
- Lack of power under load
- Check engine light, often together with P0171
Likely causes
- Vacuum or intake leaks affecting both banks
- Dirty or faulty MAF sensor
- Weak fuel delivery (pump, filter, injectors)
- PCV or intake gasket leaks
- Exhaust leak before the oxygen sensor
What to check first
- If P0171 is also present, look for a shared cause first: intake leaks and the MAF sensor
- Compare fuel trims for both banks in live data
- Inspect vacuum hoses and the intake manifold gasket
- Test fuel pressure if needed
Can you keep driving?
Drivable in the short term, but lean running stresses the engine. Have it diagnosed soon.
Scan, log and diagnose with MechanicAI
Plug a Bluetooth OBD2 adapter into your car and let MechanicAI turn raw data into answers:
- Scan, read and clear fault codes in seconds
- Inspect every sensor with live data
- Create instant logs and automatic trip records
- And above all — analyze it all with AI for the most likely cause and clear next steps.
Related codes
All information, explanations and guidance on this page are general preliminary information only. They are estimates and may be entirely wrong, incomplete or inaccurate, or may not apply to your vehicle at all. Never take any action based on this content alone — do not decide to keep driving, clear codes, replace parts, repair or otherwise work on your vehicle based only on what you read here. In every case, and for any final decision, you must consult qualified technical personnel (a professional mechanic, an authorized service centre or an engineer) and obtain their approval before acting. MechanicAI accepts no liability or responsibility whatsoever for any damage, fault, injury, loss or outcome that may arise — directly or indirectly — from using or relying on this information, for any reason and under any circumstances. By using this page you acknowledge and accept these terms.