Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P1171: Fuel System Lean During Acceleration: Description
ECM can determine if engine is running rich when vehicle operator demands heavy acceleration. When heavy acceleration is demanded, ECM will go into power enrichment mode. During this mode, a lower air/fuel ratio than 14.7:1 (around 12.0:1) will be commanded and fuel injector pulse width will increase. During this condition, ECM should detect HO2S1 signal voltage go high and remain there. DTC sets when ECM is in power enrichment mode and HO2S1 signal voltage is too low.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.