System Too Lean Bank 1
2014-2014 Lincoln MKX 3.7L V6
The 2014 Lincoln MKX is equipped with a 3.7L V6 engine. Below you'll find detailed p0171 diagnostic code information including labor time estimates, cost ranges, and technician notes specific to this engine configuration.
Description
The long-term fuel trim for Bank 1 has exceeded the positive limit, indicating the engine is running lean. The PCM is adding more fuel than normal to compensate.
Symptoms
- Check Engine Light
- Rough idle
- Hesitation on acceleration
- Poor fuel economy
- Possible misfires
- Hissing sound from vacuum leak
Common Causes
- Vacuum leak (intake manifold gasket, brake booster hose, PCV valve)
- Low fuel pressure
- Dirty or faulty MAF sensor
- Exhaust leak before O2 sensor
- Faulty O2 sensor
- Clogged fuel injector
Diagnostic Steps
- Check fuel trim values at idle and 2500 RPM
- Perform smoke test for vacuum leaks
- Test fuel pressure at idle and under load
- Clean or test MAF sensor
- Check for exhaust leaks near manifold
- Check PCV system
Repair Notes
Most common: vacuum leak. Perform smoke test first. Check MAF sensor. Test fuel pressure.
Related Codes
Other Powertrain Codes
- P0001Fuel Volume Regulator Control Circuit/Open
- P0001Fuel Volume Regulator Control Circuit/Open
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0003Fuel Volume Regulator Control Circuit Low
- P0003Fuel Volume Regulator Control Circuit Low
- P0004Fuel Volume Regulator Control Circuit High
- P0004Fuel Volume Regulator Control Circuit High
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
P0171 on Other Vehicles
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2003-2003 4.6L V8 DOHC
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2004-2004 4.6L V8 DOHC
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2005-2005 4.6L V8 DOHC
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2020-2020 3.0L Twin-Turbo V6
Lincoln Aviator
2020-2020 3.0L V6 Twin Turbo
Lincoln Aviator
2020-2020 3.0L V6 Twin Turbo Hybrid
Lincoln Aviator
2021-2021 3.0L Twin-Turbo V6
Lincoln Aviator
2021-2021 3.0L V6 Twin Turbo
Common Questions
What does code P0171 mean on a 2014-2014 Lincoln MKX?
P0171 stands for "System Too Lean Bank 1". The long-term fuel trim for Bank 1 has exceeded the positive limit, indicating the engine is running lean. The PCM is adding more fuel than normal to compensate.
What are the symptoms of P0171 on a Lincoln MKX?
Common symptoms of P0171 include: Check Engine Light, Rough idle, Hesitation on acceleration, Poor fuel economy, Possible misfires, Hissing sound from vacuum leak.
What causes P0171 on a 2014-2014 Lincoln MKX?
Common causes of P0171 include: Vacuum leak (intake manifold gasket, brake booster hose, PCV valve), Low fuel pressure, Dirty or faulty MAF sensor, Exhaust leak before O2 sensor, Faulty O2 sensor, Clogged fuel injector.
Last updated: March 2026