P0171
Medium SeveritySystem Too Lean (Bank 1)
Fuel System
What Does P0171 Mean?
The engine is running lean on bank 1 — too much air or not enough fuel. The ECM has maxed out its fuel trim trying to compensate. Common causes include vacuum leaks and dirty MAF sensors.
Common Fix
Fix vacuum leak or clean MAF sensor
Estimated Cost (DIY)
$0 - $150
Symptoms
- ⚠️Rough idle
- ⚠️Hesitation on acceleration
- ⚠️Poor fuel economy
- ⚠️Possible misfire at idle
Related Symptoms
Common Causes
How to Diagnose P0171
- 1Check for vacuum leaks with smoke test or carb cleaner
- 2Clean MAF sensor with MAF cleaner
- 3Check fuel pressure
- 4Inspect intake manifold gaskets
OEM Diagnostic Flowchart
Scroll to load technician if/then branches.
Read live data and freeze frame for P0171 to pinpoint the cause before buying parts.
Ready to fix it yourself?
Find My Vehicle Repair Guide →Select your exact vehicle for a personalized step-by-step guide
Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0171.
OEM Manual Evidence
Browse →A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL Denali AWD V8-6.2L Service Manual | Operation CHARM Operation CHARM : Car...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL Denali 2WD V8-6.2L Service Manual | Operation CHARM Operation CHARM : Car...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL 4WD V8-6.0L Service Manual | Operation CHARM Operation CHARM : Car repair...
A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Yukon XL 4WD V8-5.3L Service Manual | Operation CHARM Operation CHARM : Car repair...
Related Symptoms
Browse →Exact Vehicle Hubs
Browse →Open the exact vehicle hub for a repair workflow commonly associated with P0171.
Open the exact vehicle hub for a repair workflow commonly associated with P0171.
Open the exact vehicle hub for a repair workflow commonly associated with P0171.
Open the exact vehicle hub grounded by OEM manual evidence related to P0171.
Open the exact vehicle hub grounded by OEM manual evidence related to P0171.
Open the exact vehicle hub grounded by OEM manual evidence related to P0171.
Exact Repair Workflows
Browse →Open the exact repair flow most commonly associated with P0171 on this vehicle.
Open the exact repair flow most commonly associated with P0171 on this vehicle.
Open the exact repair flow most commonly associated with P0171 on this vehicle.
Open the exact repair flow most commonly associated with P0171 on this vehicle.
Open the exact repair flow most commonly associated with P0171 on this vehicle.
Open the exact repair flow most commonly associated with P0171 on this vehicle.
Related Codes
Same as P0171 but on bank 2. If both P0171 and P0174 are present, the issue is likely shared (MAF, fuel pump, or large vacuum leak).
Bank 1 is running rich — too much fuel relative to air. The ECM cannot trim enough fuel out to compensate.
The MAF sensor is reading outside the expected range for current engine conditions. Could be dirty, defective, or have an air leak after the sensor.
Frequently Asked Questions
- Can I drive with P0171?
- You can drive but the engine runs lean, which causes poor performance and can damage the catalytic converter over time.
- What is the most common cause of P0171?
- A vacuum leak (cracked hose, loose clamp, or leaking intake gasket) is the #1 cause, followed by a dirty MAF sensor.
Related Repair Guides
If your vehicle has triggered P0171, these DIY repair guides may help: