P0171 Ford Bronco Sport
System Too Lean (Bank 1) · Powertrain Code · High · Repair: Easy
What is P0171?
The engine is running lean on bank 1 — too much air or not enough fuel. Common causes include vacuum leaks, weak fuel pump, clogged fuel injectors, or a faulty MAF sensor.
When the Ford Bronco Sport triggers code P0171 (system too lean (bank 1)), it typically points to an issue in the powertrain system. This is a high severity code, so address it promptly to avoid further damage or safety concerns. Below you'll find the most common causes, symptoms, and repair options specific to the Ford Bronco Sport.
This repair is rated easy, meaning basic tools, no lift needed.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Ford Bronco Sport.
Common Causes on Ford Bronco Sport
- Turbo inlet pipe seal leak on 1.5L EcoBoost Escape/Bronco Sport causing lean condition
- PCV valve failure on 1.5L EcoBoost three-cylinder allowing vacuum leak
- Charge air pipe clamp loosening on turbo outlet causing boost leak on 2.0L EcoBoost
- MAF sensor contamination from oil vapor on 1.5L turbo with PCV issue
- Intake manifold gasket seepage on 2.5L naturally aspirated Escape
Symptoms
- Rough or unstable idle speed
- Hesitation or stumble during acceleration
- Engine surging or hunting at idle
- Lean misfire under load causing jerking
- Poor acceleration response and reduced power
- Check engine light illuminated
Notes for Ford Bronco Sport
Boost system leaks are the primary P0171 cause on turbo Escape and Bronco Sport models.